Add HTTPLocalRateLimitPolicy support

[alpeb]

This adds the HTTPLocalRateLimitPolicy CRD, which is indexed by the policy controller and exposed by the inbound API.

• 47e4807: HTTPLocalRateLimitPolicy CRD and related changes
• 0b99fd8: policy controller central changes
• ec8cc1c: rust tests updates and additions
• 0a4fd28: temporary dependency override on linkerd2-proxy-api to pick changes from Add support for HTTP local rate limiting linkerd2-proxy-api#388
• c10f9a8: golden files updates.

Testing

In a cluster with linkerd and emojivoto injected, deploy these resources:

 apiVersion: policy.linkerd.io/v1beta3
kind: Server
metadata:
  namespace: emojivoto
  name: web-http
spec:
  # permissive policy, so we don't require setting up authz
  accessPolicy: all-unauthenticated
  podSelector:
    matchLabels:
      app: web-svc
  port: http
  proxyProtocol: HTTP/1

apiVersion: policy.linkerd.io/v1alpha1
kind: HTTPLocalRateLimitPolicy
metadata:
  namespace: emojivoto
  name: web-rl
spec:
  targetRef:
    group: policy.linkerd.io
    kind: Server
    name: web-http
  total:
    requestsPerSecond: 100
  identity:
    requestsPerSecond: 20
  overrides:
  - requestsPerSecond: 10
    clientRefs:
    - kind: ServiceAccount
      namespace: emojivoto
      name: default

$ kubectl -n emojivoto get httplocalratelimitpolicies.policy.linkerd.io
NAME     TARGET_KIND   TARGET_NAME   TOTAL_RPS   IDENTITY_RPS
web-rl   Server        web-http      100         20

Then see how the RL policy is exposed at the inbound API under the protocol section, with linkerd dg policy -n emojivoto po/web-85f6fb8564-jp67d 8080:

...
protocol:
  Kind:
    Http1:
      local_rate_limit:
        identity:
          requestsPerSecond: 20
        metadata:
          Kind:
            Resource:
              group: policy.linkerd.io
              kind: httplocalratelimitpolicy
              name: web-rl
        overrides:
        - clients:
            identities:
            - name: default.emojivoto.serviceaccount.identity.linkerd.cluster.local
          limit:
            requestsPerSecond: 10
        total:
          requestsPerSecond: 100
...