Added previously prepared indexes for issues to sort on closed_at

What does this MR do and why?

Related to #365463 (closed).

This MR is a follow-up from !89606 (merged), where I prepared the indexes to speed up the performance when sorting issues by their closed_at filed. With this MR those indexes are actually created.

Warning: before merging we have to make sure that the indexes preparation has been successfully completed in production.

Screenshots or screen recordings

Timings to apply the migration:

main: == 20220620151740 AddIndexesIssuesOnProjectIdAndClosedAt: migrating ===========
main: -- transaction_open?()
main:    -> 0.0000s
main: -- index_exists?(:issues, "project_id, closed_at DESC NULLS LAST, state_id, id", {:name=>"index_issues_on_project_id_closed_at_desc_state_id_and_id", :algorithm=>:concurrently})
main:    -> 0.0243s
main: -- execute("SET statement_timeout TO 0")
main:    -> 0.0005s
main: -- add_index(:issues, "project_id, closed_at DESC NULLS LAST, state_id, id", {:name=>"index_issues_on_project_id_closed_at_desc_state_id_and_id", :algorithm=>:concurrently})
main:    -> 0.0021s
main: -- execute("RESET statement_timeout")
main:    -> 0.0006s
main: -- transaction_open?()
main:    -> 0.0000s
main: -- index_exists?(:issues, [:project_id, :closed_at, :state_id, :id], {:name=>"index_issues_on_project_id_closed_at_state_id_and_id", :algorithm=>:concurrently})
main:    -> 0.0243s
main: -- add_index(:issues, [:project_id, :closed_at, :state_id, :id], {:name=>"index_issues_on_project_id_closed_at_state_id_and_id", :algorithm=>:concurrently})
main:    -> 0.0015s
main: -- transaction_open?()
main:    -> 0.0000s
main: -- indexes(:issues)
main:    -> 0.0250s
main: -- remove_index(:issues, {:algorithm=>:concurrently, :name=>"index_issues_on_project_id_and_closed_at"})
main:    -> 0.0020s
main: == 20220620151740 AddIndexesIssuesOnProjectIdAndClosedAt: migrated (0.0960s) ==

Timings to revert the migration:

main: == 20220620151740 AddIndexesIssuesOnProjectIdAndClosedAt: reverting ===========
main: -- transaction_open?()
main:    -> 0.0000s
main: -- index_exists?(:issues, [:project_id, :closed_at], {:name=>"index_issues_on_project_id_and_closed_at", :algorithm=>:concurrently})
main:    -> 0.0221s
main: -- execute("SET statement_timeout TO 0")
main:    -> 0.0004s
main: -- add_index(:issues, [:project_id, :closed_at], {:name=>"index_issues_on_project_id_and_closed_at", :algorithm=>:concurrently})
main:    -> 0.0019s
main: -- execute("RESET statement_timeout")
main:    -> 0.0007s
main: -- transaction_open?()
main:    -> 0.0000s
main: -- indexes(:issues)
main:    -> 0.0244s
main: -- current_schema()
main:    -> 0.0004s
main: -- transaction_open?()
main:    -> 0.0000s
main: -- indexes(:issues)
main:    -> 0.0255s
main: -- current_schema()
main:    -> 0.0003s
main: == 20220620151740 AddIndexesIssuesOnProjectIdAndClosedAt: reverted (0.0878s) ==

How to set up and validate locally

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

MR acceptance checklist

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