edge-21.12.1

edge-21.12.1

This edge release enables by default EndpointSlices in the destination
controller, which unblocks any functionality that is specific to
EndpointSlices such as topology-aware hints. It also contains a couple of
internal cleanups and upgrades, by our external contributors!

• Added new check to linkerd check verifying the nodes aren't running the old
  Docker container runtime and attempting to run proxy-init as root at the same
  time, which doesn't work (thanks @alex-berger!)
• Enabled EndpointSlices in the destination controller by default
• Removed extraneous empty lines and fixed the formatting of warnings in the
  output of linkerd check -o short
• Upgraded to go 1.17 (thanks @Juneezee!)
• Removed old protobuf definitions from the codebase (thanks @krzysztofdrys!)