Upgrade to Go 1.22, 1.23

[abhinav]

Go 1.23 is out, so we can change supported versions to 1.22 and 1.23.
Switch CI to test against 1.22 and 1.23 only,
and merge test files that were previously split on Go versions
back together.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.42%. Comparing base (67ed361) to head (73f055e).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1235   +/-   ##
=======================================
  Coverage   98.42%   98.42%           
=======================================
  Files          35       35           
  Lines        2918     2918           
=======================================
  Hits         2872     2872           
  Misses         38       38           
  Partials        8        8           

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[rabbbit]

    strategy:
      matrix:
        go: ["stable", "oldstable"]

and then

 go-version: ${{ matrix.go }}

if: matrix.latest

below? Or do we want to control this individually?

(https://github.com/uber-go/ratelimit/blob/main/.github/workflows/test.yaml)

[JacobOaks]

Hmm... I don't have a big preference. Sometimes the latest version breaks some tests, and sometimes upgrading involves removing some old build-tagged tests (e.g., this PR). So in that vein it makes sense to make upgrading an explicit action/PR. On the other hand, this would reduce manual ops work.

[abhinav]

stable oldstable is also a valid option here. I'll defer to you on whether you want that or not.