added k_nearset_neighbors

[anishk85]

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Description

Added K-Nearest Neighbors (KNN) classification algorithm to the machine learning module.

KNN is a supervised learning algorithm that classifies data points based on the majority vote of their k nearest neighbors using Euclidean distance.

Reference: https://en.wikipedia.org/wiki/K-nearest_neighbors_algorithm

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• I ran below commands using the latest version of rust nightly.
• I ran cargo clippy --all -- -D warnings just before my last commit and fixed any issue that was found.
• I ran cargo fmt just before my last commit.
• I ran cargo test just before my last commit and all tests passed.
• I added my algorithm to the corresponding mod.rs file within its own folder, and in any parent folder(s).
• I added my algorithm to DIRECTORY.md with the correct link.
• I checked CONTRIBUTING.md and my code follows its guidelines.

Note: All 8 tests pass in <50ms (no #[ignore] needed).

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 99.40120% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 95.36%. Comparing base (ed7a42e) to head (fe19414).

Files with missing lines	Patch %	Lines
src/machine_learning/k_nearest_neighbors.rs	99.39%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #923      +/-   ##
==========================================
+ Coverage   95.32%   95.36%   +0.03%     
==========================================
  Files         319      320       +1     
  Lines       20899    21060     +161     
==========================================
+ Hits        19923    20083     +160     
- Misses        976      977       +1     

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[anishk85]

@imp2002 have you merged the files earlier without all workflows cleared because my build is failing because of the earlier issues in files