proxy: v2.114.0 (#5062)

This release overhauls the discovery and routing logic implemented by
the proxy: instead of looking at HTTP request metadata for service
discovery, the outbound proxy now exclusively use each connection's
target IP:PORT. This eager resolution eliminates per-request cache
binding; and supports using TrafficSplit with non-HTTP services.

This has a few side effects:

- The `l5d-dst-override` header is no longer honored.
- When the application attempts to connect to a pod IP, the proxy no
  longer load balances these requests among all pods in the service.
  The proxy will now honor session-stickiness as selected by an
  application-level load balancer.
- `TrafficSplits` are only applied when a client targets a service's IP.
- The proxy no longer performs DNS "canonicalization" to translate
  relative host header names to a fully-qualified form.

---

* Unify RequestFilter and Admit middlewares (linkerd/linkerd2-proxy#692)
* Only allow name-based profile discovery for inbound requests (linkerd/linkerd2-proxy#695)
* outbound: initial tests for TCP mTLS (with fewer moving parts) (linkerd/linkerd2-proxy#693)
* Stop honoring DESTINATION_GET_* configuration (linkerd/linkerd2-proxy#696)
* stack: add SwitchReady service (linkerd/linkerd2-proxy#694)
* telemetry: Remove trailing comma in build_info labels (linkerd/linkerd2-proxy#699)
* Update Rust to 1.47.0 (linkerd/linkerd2-proxy#701)
* cache: Delete benchmarks (linkerd/linkerd2-proxy#705)
* outbound: Discover profiles for each unique TCP target (linkerd/linkerd2-proxy#704)