Refactor code to use Go 1.20 and 1.21 features

[spencerschrock]

Serves as a general tracking issue for clean ups I'd like to investigate when I have time, now that 1.20 and 1.21 have new features.

1.21:

• min, max built-ins
  • we only call math.Max or math.Min in 1-2 places, but could replace that
• The new slices package can replace our use of golang.org/x/exp/slices
• The new OnceFunc, OnceValue and OnceValues could replace some of client handlers.
  • We often use sync.Once and save the response, as well as an error

1.20:

• wrapping multiple errors
  • there's a TODO in our linter config that would highlight places we can apply the change.

[github-actions]

This issue is stale because it has been open for 60 days with no activity.

[spencerschrock]

Not going to switch the sync.Once uses over, as the overall readability didn't improve too much. Can re-visit later if needed