feat: introduce metrics for serde

[MrCroxx]

What's changed and what's your intention?

Please explain IN DETAIL what the changes are in this PR and why they are needed. :D

As title. Maybe add a switch later.

Checklist

• I have written the necessary rustdoc comments
• I have added the necessary unit tests and integration tests
• I have passed make all (or make fast instead if the old tests are not modified) in my local environment.

Related issues or PRs (optional)

[codecov]

Codecov Report

Attention: Patch coverage is 97.22222% with 1 line in your changes missing coverage. Please review.

Files	Patch %	Lines
foyer-storage/src/large/scanner.rs	66.66%	1 Missing ⚠️

Files	Coverage Δ
foyer-common/src/metrics.rs	97.02% <100.00%> (+0.12%)	⬆️
foyer-storage/src/large/generic.rs	89.13% <100.00%> (+0.31%)	⬆️
foyer-storage/src/large/reclaimer.rs	86.08% <100.00%> (+0.24%)	⬆️
foyer-storage/src/large/recover.rs	90.84% <100.00%> (+0.13%)	⬆️
foyer-storage/src/serde.rs	100.00% <ø> (ø)
foyer-storage/src/store.rs	74.65% <100.00%> (+0.43%)	⬆️
foyer-storage/src/test_utils.rs	88.67% <100.00%> (+0.67%)	⬆️
foyer-storage/src/large/scanner.rs	68.65% <66.66%> (-0.29%)	⬇️

... and 1 file with indirect coverage changes