Adjust SQL and transaction Prometheus buckets

What does this MR do?

This adjusts the Prometheus buckets for SQL and transaction timings, allowing us to more precisely calculate Apdex scores. For example, for SQL timings we want a target time of 100 ms, but allow up to 250 ms. This means that for apdex, our target time is 100 ms and the desirable time 250 ms. Previously we'd be forced to using a desirable time of 1 second, which is way too high.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Conform by the code review guidelines
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing themd
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

• https://gitlab.com/gitlab-com/infrastructure/issues/1962
• gitlab-com/database#54 (moved)
• gitlab-com/database#20 (moved) (we want to use apdex scores for this)