Add find previous power of two implementation

[AliAlimohammadi]

Description

This PR adds an implementation to find the largest power of two less than or equal to a given number.

Type of change

• New algorithm implementation

Changes

• Added find_previous_power_of_two.rs with comprehensive documentation
• Includes 10 test functions with multiple test cases
• Uses efficient bit-shifting algorithm
• Follows Rust best practices and TheAlgorithms conventions

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Additional context

The algorithm uses bit shifting for $O(log n)$ time complexity.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.68%. Comparing base (e5bceac) to head (a2225d0).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #969      +/-   ##
==========================================
+ Coverage   95.67%   95.68%   +0.01%     
==========================================
  Files         342      343       +1     
  Lines       22330    22412      +82     
==========================================
+ Hits        21364    21445      +81     
- Misses        966      967       +1     

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[AliAlimohammadi]

@siriak, this is ready to be merged.

[siriak]

Looks good, thanks!