NF: rename misleading `--path` flag for `new`, `set`, and `unset`

[aqw]

These commands each used --path:

• new: -> --path (now matches the directory pseudo key)
• set: -> --asset (only operates on assets as of #557)
• unset -> --asset (only operates on assets as of #557)

This PR also:

• Removes no-op "types" from argparse that we were using to expose information to the tab completion script generation. That's all static now, so these are unused.
• Converts many short opts to long opts in the tests. They may the text more readable and thus self-documenting..

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 98.41270% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 95.68%. Comparing base (74a2f90) to head (e472193).

Files	Patch %	Lines
onyo/lib/commands.py	90.90%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #603 +/- ## ========================================== - Coverage 95.70% 95.68% -0.02% ========================================== Files 71 71 Lines 5608 5586 -22 Branches 1090 1090 ========================================== - Hits 5367 5345 -22 Misses 141 141 Partials 100 100 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[TobiasKadelka]

LGTM, thanks!