change: get dimensions for aq.ArrayVar automatically

[Yash-10]

Issue #13:

Description of changes:

• In the definition of ArrayVar in types.py, the dimensions keyword argument is no longer required but inferred from the initial expression. The initial expression, however, becomes a necessary argument following the comments made on the issue.
• args[0] is used because _ClassicalVar in oqpy's ArrayVar suggests init_expression is the first argument.

Testing done: Yes.

Merge Checklist

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General

• I have read the CONTRIBUTING doc
• I used the commit message format described in CONTRIBUTING
• I have updated any necessary documentation, including READMEs and API docs (if appropriate)
  • Perhaps not required since the high-level interface only contains args and kwargs, which remain unchanged?

Tests

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (ecce2bc) to head (1b85446).
Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #22   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           44        43    -1     
  Lines         1936      1903   -33     
  Branches       319       320    +1     
=========================================
- Hits          1936      1903   -33     

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[rmshaffer]

This is looking good - thank you for taking this on! Just a few small comments and suggestions.

[rmshaffer]

This is looking good! Couple of minor suggestions but after that I think this will be ready to go.