pw_rpc.console_tools: Support aliasing renamed commands

- The alias_deprecated_command function creates an alias that redirects
  from an old RPC command name to a new name.
- Move console_tools.Watchdog tests to their own file.

Change-Id: Ie7071462e5c17e5782fb549cc2f15aa19e64bbf0
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/44120
Reviewed-by: Alexei Frolov <frolv@google.com>
Commit-Queue: Wyatt Hepler <hepler@google.com>