chore: use oldstable and stable for running workflows

[RomainMuller]

This allows us to never have to change our workflow configuration when a new go release is issued, as these labels automatically resolve via the published release manifest.

Also uses go.mod files instead of go.sum files to compute cache keys, as the go.sum files are technically not a dependency manifest.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.50%. Comparing base (9bd25ae) to head (e541fbb).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #227   +/-   ##
=======================================
  Coverage   61.50%   61.50%           
=======================================
  Files          90       90           
  Lines        4915     4915           
=======================================
  Hits         3023     3023           
  Misses       1569     1569           
  Partials      323      323           

Flag	Coverage Δ
ARM64	44.68% <ø> (ø)
Linux	66.13% <ø> (ø)
Windows	43.56% <ø> (ø)
X64	61.50% <ø> (ø)
generator	42.71% <ø> (ø)
go	50.96% <ø> (?)
go1.22	44.68% <ø> (-6.28%)	⬇️
go1.23	44.46% <ø> (-5.29%)	⬇️
integration	46.19% <ø> (ø)
macOS	44.68% <ø> (ø)
unit	41.21% <ø> (+1.20%)	⬆️

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