[Techinal Debt] Cleanup ABI vs. Tunnel CLI commands

[NO TESTS NEEDED]

This commit cleans up two issues:
* Most commands support all EngineModes so default to that. Let
  outlayers declare their intent.
* Use cobra.Annotations to set supported EngineMode. This simplies
  instantiating commands as there is now one method to communicate a
  commands requirements rather than two.
* Combined aliased commands into one file
* Fixed aliased commands where Args field did not match
* Updated examples in README.md for writing commands
* Remove redundant flag DisableFlagsInUseLine in cobra.Command
  initialization.

Signed-off-by: Jhon Honce <jhonce@redhat.com>

cmd/podman/diff.go

@@ -34,7 +34,6 @@ var (
 
 func init() {
 	registry.Commands = append(registry.Commands, registry.CliCommand{
-		Mode:    []entities.EngineMode{entities.ABIMode, entities.TunnelMode},
 		Command: diffCmd,
 	})
 	flags := diffCmd.Flags()