Prepare async index for p_ci_builds.upstream_pipeline_id and commit_id

What does this MR do and why?

Prepare async index for p_ci_builds.upstream_pipeline_id and commit_id

As titled, this is the first step of creating indexes asynchronously. See guideline at https://docs.gitlab.com/ee/development/database/adding_database_indexes.html#schedule-the-index-to-be-created

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

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Before	After

How to set up and validate locally

1. Run the following commands:

   ./scripts/regenerate-schema
   RAILS_ENV=test bin/rails runner 'Feature.enable :database_async_index_operations'
   RAILS_ENV=test bin/rake gitlab:db:execute_async_index_operations:all

2. Confirm the following indexes are created in TEST environment

   psql gitlabhq_test -h $PATH_TO_POSTGRESQL/gitlab-development-kit/postgresql

   "index_357cc39ca4" btree (commit_id_convert_to_bigint, artifacts_expire_at, id) WHERE type::text = 'Ci::Build'::text AND (retried = false OR retried IS NULL) AND (name::text = ANY (ARRAY['sast'::character varying::text, 'secret_detection'::character varying::text, 'dependency_scanning'::character varying::text, 'container_scanning'::character varying::text, 'dast'::character varying::text]))
   "index_89477d6012" btree (upstream_pipeline_id_convert_to_bigint) WHERE upstream_pipeline_id_convert_to_bigint IS NOT NULL
   "index_fc42f73fa6" btree (commit_id_convert_to_bigint, type, ref)

3. Run the following commands to restore the feature flag:

   RAILS_ENV=test bin/rails runner 'Feature.disable :database_async_index_operations'

Numbered steps to set up and validate the change are strongly suggested.

Related to #422835 (closed)