feat(maths): enhance Average with stream method and improved JavaDoc

[Papichardog]

Description

Enhanced the Average.java utility class in the com.thealgorithms.maths package with two improvements:

• Improved JavaDoc comments on existing methods, clarifying truncation behavior on average(int[]) and adding @throws documentation.
• Added a new averageStream(double[]) method using the Java Stream API as a modern, declarative alternative. Returns OptionalDouble following Stream API conventions.

Checklist

• 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 algorithms include a corresponding test class that validates their functionality.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.51%. Comparing base (49f9e1a) to head (a93fca0).

Files with missing lines	Patch %	Lines
src/main/java/com/thealgorithms/maths/Average.java	0.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7369      +/-   ##
============================================
- Coverage     79.51%   79.51%   -0.01%     
- Complexity     7142     7144       +2     
============================================
  Files           796      796              
  Lines         23359    23362       +3     
  Branches       4596     4596              
============================================
+ Hits          18575    18577       +2     
- Misses         4046     4049       +3     
+ Partials        738      736       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.