This edge release introduces several changes around metrics. ReplicaSets are now a supported resource and metrics can be associated with them. A new metric has been added which counts proxy errors encountered before a protocol can be detected. Finally, the request errors metric has been split into separate inbound and outbound directions. * Fixed printing `check --pre` command usage if it fails after being unable to connect to Kubernetes (thanks @rdileep13!) * Updated the default skip and opaque ports to match that which is listed in the [documentation](https://linkerd.io/2.10/features/protocol-detection/#configuring-protocol-detection) * Added the `LINKERD2_PROXY_INBOUND_PORTS` environment variable during proxy injection which will be used by ongoing policy changes * Added client-go cache size metrics to the `diagnostics controller-metrics` command * Added validation that the certificate provided by an external issuer is a CA (thanks @rumanzo!) * Added metrics support for ReplicaSets * Replaced the `request_errors_total` metric with two new metrics: `inbound_http_errors_total` and `outbound_http_errors_total` * Introduced the `inbound_tcp_accept_errors_total` and `outbound_tcp_accept_errors_total` metrics which count proxy errors encountered before a protocol can be detected