Most of the groundwork was laid in previous PRs between adding the cert-monitor package to extracting the logic of signing certificates out of the connect_ca_endpoint.go code and into a method on the server.
This also refactors the auto-config package a bit to split things out into multiple files.
Refactoring of the agentpb package.
First move the whole thing to the top-level proto package name.
Secondly change some things around internally to have sub-packages.
# Conflicts:
# agent/consul/state/acl.go
# agent/consul/state/acl_test.go