Add default (mold, array_size) overloads for rvs_normal

[gururaj1512]

Resolves #963

• Add convenience overloads for rvs_normal that accept (mold, array_size) and return standard-normal arrays (loc=0, scale=1) for both real and complex kinds.
• Add deterministic tests that compare the new (mold, array_size) call with the explicit (loc=0, scale=1, array_size) call to ensure identical behavior.

[gururaj1512]

@jvdp1, Can you have a look. Needs review...!

[jvdp1]

Thank you @gururaj1512 . I have some suggestions below.

[gururaj1512]

@jvdp1, I've refactored as per your suggestion.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 25.13%. Comparing base (fffe0d7) to head (6e2fd8e).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1056      +/-   ##
==========================================
+ Coverage   25.12%   25.13%   +0.01%     
==========================================
  Files         570      570              
  Lines      234201   234201              
  Branches    41277    41274       -3     
==========================================
+ Hits        58838    58866      +28     
+ Misses     175363   175335      -28     

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[jvdp1]

@jvdp1, I've refactored as per your suggestion.

Thank you. LGTM. Could you also update the specs, please?

[gururaj1512]

@jvdp1, Updated the specs...!