chore: update go-grpc-prometheus middleware to use fork with grpc_code

[jon-whit]

Description

Switches from the now deprecated github.com/grpc-ecosystem/go-grpc-prometheus package to a forked version github.com/jon-whit/go-grpc-prometheus. The fork includes changes that add the grpc_code label to the grpc_server_handling_seconds histogram.

The newer upstream project github.com/grpc-ecosystem/go-grpc-middleware/providers/prometheus also does not yet have the grpc_code included in the grpc_server_handling_seconds histogram. There doesn't seem to be consensus on if that label should be added, but since we need it to define sensible SLOs, we forked and added it.

Here's a screenshot of these changes in action:

References

Related issues:
grpc-ecosystem/go-grpc-middleware#606
grpc-ecosystem/go-grpc-prometheus#75

Review Checklist

• I have clicked on "allow edits by maintainers".
• I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• The correct base branch is being used, if not main
• I have added tests to validate that the change in functionality is working as expected

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.10% ⚠️

Comparison is base (6efcac9) 82.20% compared to head (609f447) 82.09%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #895      +/-   ##
==========================================
- Coverage   82.20%   82.09%   -0.10%     
==========================================
  Files          64       64              
  Lines        7666     7666              
==========================================
- Hits         6301     6293       -8     
- Misses       1065     1070       +5     
- Partials      300      303       +3     

Files Changed	Coverage Δ
cmd/run/run.go	72.04% <ø> (+0.33%)	⬆️

... and 4 files with indirect coverage changes

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