Extend utilities for checking a scalar value

[gramalingam]

Extend the is_singleton_value utility to check for singleton values that may be either 0D or 1D tensors.

[codecov]

Codecov Report

❌ Patch coverage is 44.44444% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.06%. Comparing base (dddf0c2) to head (051b30b).
⚠️ Report is 5 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
onnxscript/rewriter/_ir_utils.py	57.14%	2 Missing and 1 partial ⚠️
...xscript/rewriter/rules/fusion/_rotary_embedding.py	0.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2587      +/-   ##
==========================================
+ Coverage   70.04%   70.06%   +0.02%     
==========================================
  Files         223      223              
  Lines       26215    26263      +48     
  Branches     2583     2601      +18     
==========================================
+ Hits        18363    18402      +39     
- Misses       6946     6950       +4     
- Partials      906      911       +5     

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