refactor: optimize ValidParentheses methods and add parameterized tests

[alxkm]

• Simplified stack-based logic for better readability and efficiency
• Combined similar validation approaches into clearer methods
• Added parameterized tests covering diverse valid and invalid cases
• Improved error handling for unexpected characters with informative exceptions

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

❌ Patch coverage is 60.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.62%. Comparing base (fa2ca9d) to head (2588cdc).
⚠️ Report is 381 commits behind head on master.

Files with missing lines	Patch %	Lines
...va/com/thealgorithms/strings/ValidParentheses.java	60.00%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6352      +/-   ##
============================================
+ Coverage     74.60%   74.62%   +0.01%     
+ Complexity     5453     5449       -4     
============================================
  Files           682      682              
  Lines         19030    19017      -13     
  Branches       3683     3677       -6     
============================================
- Hits          14198    14191       -7     
+ Misses         4270     4269       -1     
+ Partials        562      557       -5     

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