fix(metrics): bound HTTP method label cardinality

[GatewayJ]

Type of Change

• New Feature
• Bug Fix
• Documentation
• Performance Improvement
• Test/CI
• Refactor
• Other:

Related Issues

Fixes rustfs/backlog#1097

Summary of Changes

• normalize HTTP method labels at the shared record_http_request boundary
• preserve the nine standard HTTP methods and group all custom methods as OTHER
• keep operator and Console middleware paths on the same bounded-label rule
• add unit and Axum middleware coverage for custom-method aggregation

Checklist

• I have read and followed the CONTRIBUTING.md guidelines
• Passed make pre-commit (fmt-check + clippy + test + console-lint + console-fmt-check)
• Added/updated necessary tests
• Documentation: N/A; the exported metric name and label keys are unchanged
• CHANGELOG: N/A; this is a metrics cardinality hardening fix
• CI/CD passed (pending GitHub Actions)

Impact

• Breaking change (CRD/API compatibility)
• Requires doc/config/deployment update
• Other impact: custom HTTP method series are consolidated under method="OTHER"

Verification

make pre-commit

Additional Notes

Normalization happens before both the counter and duration-summary maps are updated, so untrusted method values cannot create persistent metric series. Existing standard-method labels remain unchanged.

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