PERF: Cache Route Pattern Once Per Request Across Policies

[MrEthical07]

Background:
Both cache and rate limit policies resolve route pattern independently on the same request path. On high RPS routes with chained policies, this duplicates work on a hot path.

Problem:
Route pattern extraction is repeated in internal/core/policy/cache.go and internal/core/policy/ratelimit.go, increasing per-request overhead.

Scope:

• Introduce a per-request route pattern resolver/cache in policy flow.
• Update cache and rate limit policies to reuse the same resolved value.
• Add a benchmark case for chained policy execution in internal/core/policy/benchmark_test.go.

Tasks:

• Add helper to resolve and store route pattern once per request context.
• Replace duplicate route resolution calls in cache and rate limit policies.
• Add benchmark coverage for cache+ratelimit chain.
• Add regression tests for correctness.

Acceptance Criteria:

• Route pattern is resolved at most once per request in chained policy scenarios.
• Behavior and response semantics remain unchanged.
• Benchmark shows reduced ns/op for policy chain path.