Feature/issue 465 coverage for hash table and tim sorter

[gmottajr]

Added tests for HashTable to improve coverage of key behaviors

1. **Add_ShouldTriggerResize_WhenThresholdExceeded:** Verifies that the HashTable triggers a resize when the number of elements exceeds the initial capacity.
   

2. **Add_ThrowsException_WhenKeyIsDefault:** Ensures that adding a key with the default value (e.g., 0 for integers) throws an ArgumentNullException, as per the Add method’s validation.
   

3. **Add_ThrowsException_WhenValueIsDefault:** Verifies that adding a value with the default value (e.g., null for reference types) throws an ArgumentNullException.
   

4. **Add_StoresValueCorrectly:** Confirms that values are correctly stored and can be retrieved via the key after an Add operation.
   

5. **Get_ReturnsCorrectValue_ForExistingKey:** Ensures that the correct value is returned when querying for an existing key.
   

6. **Get_ThrowsException_WhenKeyDoesNotExist:** Verifies that accessing a non-existent key throws a KeyNotFoundException, maintaining expected behavior.
   

7. **Capacity_Increases_WhenResizeOccurs:** Checks that the HashTable increases its capacity when the number of items exceeds the threshold, ensuring proper resizing.
   

These tests aim to cover edge cases, resizing logic, and ensure correct behavior of the Add and Get methods, improving overall robustness and stability.

• [X ] I have performed a self-review of my code
• My code follows the style guidelines of this project
• [X ] I have added tests that prove my fix is effective or that my feature works
• [X ] New and existing unit tests pass locally with my changes
• [X ] 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 95.16%. Comparing base (0ef9849) to head (41a421f).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #500      +/-   ##
==========================================
+ Coverage   95.11%   95.16%   +0.04%     
==========================================
  Files         267      267              
  Lines       10848    10848              
  Branches     1527     1527              
==========================================
+ Hits        10318    10323       +5     
+ Misses        403      400       -3     
+ Partials      127      125       -2     

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[siriak]

Looks good, thanks!

You can also see in coverage report that coverage also fluctuates in FastSearcher