This change adds comments to exported things and renames the tcp,
http, and exec probe interfaces to just be Prober within their
namespace.
Issue #68026
etcd has support for client-cert-auth, which can be configured via the flag `--ca-file`,
when that is enabled, all the client requests must present with a client certificate,
however, the current component status check uses a single transport for all of the checks,
this is wrong, the checks should be different for each of different component, and make
each of them use different transport(tls configurations).
