Atmos custom subcommands may shadow built-in subcommands (e.g. `atmos terraform state`)

[osterman]

Describe the Bug

If you create a custom subcommand, that has the same arguments as a built-in command, the built-in command is "lost".

e.g.

If we create a custom subcommand atmos terraform state foobar, then all of the built-in atmos terraform state * commands stop working (cannot be found).

Expected Behavior

We should support some order of precedence, and support both. If a custom command is defined, then it would take precedence. Also, all other built-in commands should continue to work.

Steps to Reproduce

See above.

Screenshots

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Environment

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Additional Context

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