Replace hardcoded table names with arel values

What does this MR do and why?

Related to #358943 (closed)

I've noticed this while working on !92440 (diffs, comment 1026630646) and it's something worth fixing for the future work on CI data partitioning.

Before:

[2] pry(main)> Ci::Pipeline.created_after(1.day.ago).to_sql
=> "SELECT \"ci_pipelines\".* FROM \"ci_pipelines\" WHERE (ci_pipelines.created_at > '2022-07-14 10:22:28.708263')"
[3] pry(main)> Ci::Pipeline.created_before_id(1000).to_sql
=> "SELECT \"ci_pipelines\".* FROM \"ci_pipelines\" WHERE (ci_pipelines.id < 1000)"

After:

[1] pry(main)> Ci::Pipeline.created_after(1.day.ago).to_sql
=> "SELECT \"ci_pipelines\".* FROM \"ci_pipelines\" WHERE \"ci_pipelines\".\"created_at\" > '2022-07-14 10:27:51.214217'"
[2] pry(main)> Ci::Pipeline.created_before_id(1000).to_sql
=> "SELECT \"ci_pipelines\".* FROM \"ci_pipelines\" WHERE \"ci_pipelines\".\"id\" < 1000"

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