`disable_statement_timeout` will no longer leak to other migrations

What does this MR do?

Adds transaction: true/false (defaults to true) to disable_statement_timeout. This controls whether SET LOCAL will be used to define statement_timeout value to 0.

When transaction: false it requires a block, so the code inside the block will be executed with "disabled statement timeout", after it executes it cleans up connection state with RESET ALL.

Are there points in the code the reviewer needs to double check?

Please double-check if I enclosed the right pieces while fixing existing migrations.

The EE build is in here: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/6444 with any extra fix required in separate commits.

Why was this MR needed?

Using disable_statement_timeout can leak to other transactions and queries inside the same connection, until connection is closed or RESET ALL is called (from pgbouncer using isolation: transaction)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a Database specialist
• Conform by the merge request performance guides
• Conform by the style guides
• Conform by the database guides
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #48967 (closed)