chore: add GlobalUsings.cs with project-wide using directives in algorithms tests

[KaranChadha10]

Description

This pull request contains the following changes

• Converted block-scoped namespaces to file-scoped namespaces for consistency in Algorithms.Tests folder
• Removed redundant/unused global using directives to improve code clarity
• Aligned code formatting with project conventions and C# 10+ style guidelines

Issue Link: #520

• I have performed a self-review of my code
• My code follows the style guidelines of this project
• 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
• Comments in areas I changed are up to date
• I have added comments to hard-to-understand areas of my code
• I have made corresponding changes to the README.md

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.19%. Comparing base (d6c0553) to head (d6a99a0).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #524   +/-   ##
=======================================
  Coverage   95.18%   95.19%           
=======================================
  Files         272      272           
  Lines       10921    10921           
  Branches     1536     1536           
=======================================
+ Hits        10395    10396    +1     
  Misses        400      400           
+ Partials      126      125    -1     

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[Copilot]

Pull Request Overview

This PR refactors the test codebase by introducing global using directives to reduce redundant imports. The changes consolidate commonly used namespaces into a centralized GlobalUsings.cs file and remove repetitive using statements across test files.

• Adds a GlobalUsings.cs file with project-wide using directives for commonly used namespaces
• Removes redundant using statements from all test files in the Algorithms.Tests folder
• Maintains consistent code formatting and file-scoped namespace usage

Reviewed Changes

Copilot reviewed 205 out of 205 changed files in this pull request and generated 3 comments.

File	Description
Algorithms.Tests/GlobalUsings.cs	New file containing global using directives for System, Collections, LINQ, testing frameworks, and utilities
Multiple test files across all test directories	Removed redundant using statements that are now globally available

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[siriak]

Looks good, thanks!