Preload Ci::Runner tags to prevent N+1 queries [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

Contributes to #21107 (closed)

Preloads Ci::Runner tags on "Settings > CI/CI" page.

In a nutshell, the queries look:

Before

> Ci::Runner.all.map { |r| r.tags }

  Ci::Runner Load (0.8ms)  SELECT "ci_runners".* FROM "ci_runners" 
  ActsAsTaggableOn::Tag Load (0.4ms)  SELECT "tags".* FROM "tags" INNER JOIN "taggings" ON "tags"."id" = "taggings"."tag_id" WHERE "taggings"."taggable_id" = 1 AND "taggings"."taggable_type" = 'Ci::Runner' AND "taggings"."context" = 'tags' 
  ActsAsTaggableOn::Tag Load (0.3ms)  SELECT "tags".* FROM "tags" INNER JOIN "taggings" ON "tags"."id" = "taggings"."tag_id" WHERE "taggings"."taggable_id" = 2 AND "taggings"."taggable_type" = 'Ci::Runner' AND "taggings"."context" = 'tags' 
  ActsAsTaggableOn::Tag Load (0.3ms)  SELECT "tags".* FROM "tags" INNER JOIN "taggings" ON "tags"."id" = "taggings"."tag_id" WHERE "taggings"."taggable_id" = 3 AND "taggings"."taggable_type" = 'Ci::Runner' AND "taggings"."context" = 'tags' 
  ActsAsTaggableOn::Tag Load (0.3ms)  SELECT "tags".* FROM "tags" INNER JOIN "taggings" ON "tags"."id" = "taggings"."tag_id" WHERE "taggings"."taggable_id" = 4 AND "taggings"."taggable_type" = 'Ci::Runner' AND "taggings"."context" = 'tags' 
  ActsAsTaggableOn::Tag Load (0.3ms)  SELECT "tags".* FROM "tags" INNER JOIN "taggings" ON "tags"."id" = "taggings"."tag_id" WHERE "taggings"."taggable_id" = 5 AND "taggings"."taggable_type" = 'Ci::Runner' AND "taggings"."context" = 'tags' 
  ActsAsTaggableOn::Tag Load (0.3ms)  SELECT "tags".* FROM "tags" INNER JOIN "taggings" ON "tags"."id" = "taggings"."tag_id" WHERE "taggings"."taggable_id" = 6 AND "taggings"."taggable_type" = 'Ci::Runner' AND "taggings"."context" = 'tags' 

After

> Ci::Runner.all.with_tags.map { |r| r.tags }

  Ci::Runner Load (0.3ms)  SELECT "ci_runners".* FROM "ci_runners" 
  ActsAsTaggableOn::Tagging Load (0.4ms)  SELECT "taggings".* FROM "taggings" WHERE "taggings"."taggable_type" = 'Ci::Runner' AND "taggings"."context" = 'tags' AND "taggings"."taggable_id" IN (1, 2, 3, 4, 5, 6)
  ActsAsTaggableOn::Tag Load (0.2ms)  SELECT "tags".* FROM "tags" WHERE "tags"."id" IN (5, 4, 3, 2, 1) 

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

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• 📋 Does this MR need a changelog?
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• [-] Documentation (if required)
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• [-] Separation of EE specific content

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• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
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• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
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