feat(cache): add pingora-cache integration with per-route config

Add in-memory HTTP response cache using pingora-cache MemCache backend.
Cache runs after the detection pipeline so cache hits bypass upstream
request modifications and body rewriting. Respects Cache-Control
(no-store, private, s-maxage, max-age), skips caching for routes with
body rewrites or auth subrequest headers, and supports configurable
default TTL, stale-while-revalidate, and max file size per route.

Signed-off-by: Sienna Meridian Satterwhite <sienna@sunbeam.pt>

Cargo.lock

@@ -3584,6 +3584,7 @@ dependencies = [
  "opentelemetry_sdk",
  "pin-project-lite",
  "pingora",
+ "pingora-cache",
  "pingora-core",
  "pingora-http",
  "pingora-proxy",