Remove cross-join from `Ci::Runner#projects`

What does this MR do and why?

This MR adds disable_joins to the ::Ci::Runner#projects association under the new ci_runner_has_many_projects_disable_joins feature flag.

Queries

BEFORE

SELECT "projects"."id", "projects"."name", "projects"."path", "projects"."description", "projects"."created_at", 
"projects"."updated_at", "projects"."creator_id", "projects"."namespace_id", "projects"."last_activity_at", 
"projects"."import_url", "projects"."visibility_level", "projects"."archived", "projects"."avatar", 
"projects"."merge_requests_template", "projects"."star_count", "projects"."merge_requests_rebase_enabled", 
"projects"."import_type", "projects"."import_source", "projects"."approvals_before_merge", 
"projects"."reset_approvals_on_push", "projects"."merge_requests_ff_only_enabled", "projects"."issues_template", 
"projects"."mirror", "projects"."mirror_user_id", "projects"."shared_runners_enabled", "projects"."runners_token", 
"projects"."build_coverage_regex", "projects"."build_allow_git_fetch", "projects"."build_timeout", 
"projects"."mirror_trigger_builds", "projects"."pending_delete", "projects"."public_builds", 
"projects"."last_repository_check_failed", "projects"."last_repository_check_at", 
"projects"."only_allow_merge_if_pipeline_succeeds", "projects"."has_external_issue_tracker", "projects"."repository_storage",
 "projects"."repository_read_only", "projects"."request_access_enabled", "projects"."has_external_wiki", 
"projects"."ci_config_path", "projects"."lfs_enabled", "projects"."description_html", 
"projects"."only_allow_merge_if_all_discussions_are_resolved", "projects"."repository_size_limit", 
"projects"."printing_merge_request_link_enabled", "projects"."auto_cancel_pending_pipelines", 
"projects"."service_desk_enabled", "projects"."cached_markdown_version", "projects"."delete_error", 
"projects"."last_repository_updated_at", "projects"."disable_overriding_approvers_per_merge_request", 
"projects"."storage_version", "projects"."resolve_outdated_diff_discussions", 
"projects"."remote_mirror_available_overridden", "projects"."only_mirror_protected_branches", 
"projects"."pull_mirror_available_overridden", "projects"."jobs_cache_index", 
"projects"."external_authorization_classification_label", "projects"."mirror_overwrites_diverged_branches", 
"projects"."pages_https_only", "projects"."external_webhook_token", "projects"."packages_enabled", 
"projects"."merge_requests_author_approval", "projects"."pool_repository_id", "projects"."runners_token_encrypted", 
"projects"."bfg_object_map", "projects"."detected_repository_languages", 
"projects"."merge_requests_disable_committers_approval", "projects"."require_password_to_approve", 
"projects"."emails_disabled", "projects"."max_pages_size", "projects"."max_artifacts_size", 
"projects"."remove_source_branch_after_merge", "projects"."marked_for_deletion_at", 
"projects"."marked_for_deletion_by_user_id", "projects"."autoclose_referenced_issues", 
"projects"."suggestion_commit_message", "projects"."project_namespace_id" FROM "projects" INNER JOIN "ci_runner_projects" ON 
"projects"."id" = "ci_runner_projects"."project_id" WHERE "ci_runner_projects"."runner_id" = 2

AFTER

SELECT "ci_runner_projects"."project_id" FROM "ci_runner_projects" WHERE "ci_runner_projects"."runner_id" = 2

SELECT "projects"."id", "projects"."name", "projects"."path", "projects"."description", "projects"."created_at", 
"projects"."updated_at", "projects"."creator_id", "projects"."namespace_id", "projects"."last_activity_at", 
"projects"."import_url", "projects"."visibility_level", "projects"."archived", "projects"."avatar", 
"projects"."merge_requests_template", "projects"."star_count", "projects"."merge_requests_rebase_enabled", 
"projects"."import_type", "projects"."import_source", "projects"."approvals_before_merge", 
"projects"."reset_approvals_on_push", "projects"."merge_requests_ff_only_enabled", "projects"."issues_template", 
"projects"."mirror", "projects"."mirror_user_id", "projects"."shared_runners_enabled", "projects"."runners_token", 
"projects"."build_coverage_regex", "projects"."build_allow_git_fetch", "projects"."build_timeout", 
"projects"."mirror_trigger_builds", "projects"."pending_delete", "projects"."public_builds", 
"projects"."last_repository_check_failed", "projects"."last_repository_check_at", 
"projects"."only_allow_merge_if_pipeline_succeeds", "projects"."has_external_issue_tracker", "projects"."repository_storage",
 "projects"."repository_read_only", "projects"."request_access_enabled", "projects"."has_external_wiki", 
"projects"."ci_config_path", "projects"."lfs_enabled", "projects"."description_html", 
"projects"."only_allow_merge_if_all_discussions_are_resolved", "projects"."repository_size_limit", 
"projects"."printing_merge_request_link_enabled", "projects"."auto_cancel_pending_pipelines", 
"projects"."service_desk_enabled", "projects"."cached_markdown_version", "projects"."delete_error", 
"projects"."last_repository_updated_at", "projects"."disable_overriding_approvers_per_merge_request", 
"projects"."storage_version", "projects"."resolve_outdated_diff_discussions", 
"projects"."remote_mirror_available_overridden", "projects"."only_mirror_protected_branches", 
"projects"."pull_mirror_available_overridden", "projects"."jobs_cache_index", 
"projects"."external_authorization_classification_label", "projects"."mirror_overwrites_diverged_branches", 
"projects"."pages_https_only", "projects"."external_webhook_token", "projects"."packages_enabled", 
"projects"."merge_requests_author_approval", "projects"."pool_repository_id", "projects"."runners_token_encrypted", 
"projects"."bfg_object_map", "projects"."detected_repository_languages", 
"projects"."merge_requests_disable_committers_approval", "projects"."require_password_to_approve", 
"projects"."emails_disabled", "projects"."max_pages_size", "projects"."max_artifacts_size", 
"projects"."remove_source_branch_after_merge", "projects"."marked_for_deletion_at", 
"projects"."marked_for_deletion_by_user_id", "projects"."autoclose_referenced_issues", 
"projects"."suggestion_commit_message", "projects"."project_namespace_id" FROM "projects" WHERE "projects"."id" IN (1, 2)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Issues

Main issue: #338659 (closed)
Feature flag rollout issue: #342244 (closed)