feat: immutable options in random.alpha methods

[ST-DDT]

Similar to other methods I changed random.alpha() and random.alphaNumeric() to don't alter their options.

Hints for reviewers:

• I moved the default values to the method signature, to improve the api doc generation.
• I also removed the array length check, as the called method does nothing, if the array is empty, and does so almost NO-OP.
  I can re-add the check, if you insist.

[codecov]

Codecov Report

Merging #790 (6d84908) into main (612fc38) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 6d84908 differs from pull request most recent head d548757. Consider uploading reports for the commit d548757 to get more accurate results

@@            Coverage Diff             @@
##             main     #790      +/-   ##
==========================================
- Coverage   99.35%   99.35%   -0.01%     
==========================================
  Files        1921     1921              
  Lines      179109   179074      -35     
  Branches      897      902       +5     
==========================================
- Hits       177961   177922      -39     
- Misses       1092     1096       +4     
  Partials       56       56              

Impacted Files	Coverage Δ
src/random.ts	99.45% <100.00%> (-0.02%)	⬇️
src/utils/unique.ts	95.23% <0.00%> (-3.39%)	⬇️
src/unique.ts	100.00% <0.00%> (ø)

[Shinigami92]

Previously there was no failing test, please add one to test that the options are not mutated