Support --empty option for 'snapshot' command

[gshank]

Resolves #10372

Problem

The empty flag is not allowed for snapshots.

Solution

Add 'empty' to the permitted option flags.

Checklist

• I have read the contributing guide and understand what's expected of me.
• I have run this code in development, and it appears to resolve the stated issue.
• This PR includes tests, or tests are not required or relevant for this PR.
• This PR has no interface changes (e.g., macros, CLI, logs, JSON artifacts, config files, adapter interface, etc.) or this PR has already received feedback and approval from Product or DX.
• This PR includes type annotations for new and modified functions.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.08%. Comparing base (8c6bec4) to head (ef57217).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10962      +/-   ##
==========================================
- Coverage   89.15%   89.08%   -0.07%     
==========================================
  Files         183      183              
  Lines       23529    23553      +24     
==========================================
+ Hits        20977    20983       +6     
- Misses       2552     2570      +18     

Flag	Coverage Δ
integration	86.38% <100.00%> (-0.15%)	⬇️
unit	62.76% <100.00%> (+0.49%)	⬆️

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Components	Coverage Δ
Unit Tests	62.76% <100.00%> (+0.49%)	⬆️
Integration Tests	86.38% <100.00%> (-0.15%)	⬇️