Add Unity Catalog support

[pietern]

Changes w.r.t. #414:

• Hide existing commands of the form verb-noun (but keep them around for backward compatibility)
• Register commands grouped by entity, to support calling them as noun verb
• Documentation related changes (docstrings and --help output)

[codecov-commenter]

Codecov Report

Merging #471 (e730dd9) into main (dd24afa) will decrease coverage by 24.37%.
The diff coverage is 1.04%.

@@             Coverage Diff             @@
##             main     #471       +/-   ##
===========================================
- Coverage   85.22%   60.85%   -24.38%     
===========================================
  Files          42       55       +13     
  Lines        3270     4629     +1359     
===========================================
+ Hits         2787     2817       +30     
- Misses        483     1812     +1329     

Impacted Files	Coverage Δ
databricks_cli/cli.py	0.00% <0.00%> (ø)
databricks_cli/unity_catalog/api.py	0.00% <0.00%> (ø)
databricks_cli/unity_catalog/catalog_cli.py	0.00% <0.00%> (ø)
databricks_cli/unity_catalog/cli.py	0.00% <0.00%> (ø)
databricks_cli/unity_catalog/cred_cli.py	0.00% <0.00%> (ø)
databricks_cli/unity_catalog/delta_sharing_cli.py	0.00% <0.00%> (ø)
databricks_cli/unity_catalog/ext_loc_cli.py	0.00% <0.00%> (ø)
databricks_cli/unity_catalog/lineage_cli.py	0.00% <0.00%> (ø)
databricks_cli/unity_catalog/metastore_cli.py	0.00% <0.00%> (ø)
databricks_cli/unity_catalog/perms_cli.py	0.00% <0.00%> (ø)
... and 8 more

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[adamcain-db]

LGTM. I compared this branch against the latest master in databricks-cli-private and found no issues. I tried out the new command structure and it looks very good.
Thanks much for this work!

[pietern]

Incorporated a comment from @deka108 in #414 to provide a consistent --help output for --json and --json-file.

Difference introduced by 3766079: https://gist.github.com/pietern/f3bb9002b23f6cc714a561196e477e10

[adamcain-db]

@pietern: I just noticed that the files from tests/lineages were not added (see PR in databricks-cli-private repo).

[pietern]

@LuShuai Could you port these over?

[adamcain-db]

@LuShuai Could you port these over?

Added in PR #538.