core/cmd: add help-all subcommand for listing all commands

[jmank88]

This PR adds a new subcommand, chainlink help-all, that lists out all available (sub)commands.

...
   forwarders      Commands for managing forwarder addresses.
   help-all        Shows a list of all commands and sub-commands
   help, h         Shows a list of commands or help for one command
...

admin # Commands for remotely taking admin related actions
admin chpass # Change your API password remotely
admin login # Login to remote client by creating a session cookie
admin logout # Delete any local sessions
admin profile # Collects profile metrics from the node.
admin status # Displays the health of various services running inside the node.
admin users # Create, edit permissions, or delete API users
admin users chrole # Changes an API user's role
admin users create # Create a new API user
admin users delete # Delete an API user
admin users list # Lists all API users and their roles
attempts # Commands for managing Ethereum Transaction Attempts
attempts list # List the Transaction Attempts in descending order
...

[github-actions]

I see that you haven't updated any README files. Would it make sense to do so?

[cl-sonarqube-production]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube