[Smart Hashing] Cleanup

[harsh-joshi99]

Cleanup for smart hashing util.
Remove destination slugs and feature flag.

Testing

Include any additional information about the testing you have completed to
ensure your changes behave as expected. For a speedy review, please check
any of the tasks you completed below during your testing.

• Added unit tests for new functionality
• Tested end-to-end using the local server
• [If destination is already live] Tested for backward compatibility of destination. Note: New required fields are a breaking change.
• [Segmenters] Tested in the staging environment
• [Segmenters] [If applicable for this change] Tested for regression with Hadron.

[codecov]

Codecov Report

Attention: Patch coverage is 89.04110% with 8 lines in your changes missing coverage. Please review.

Project coverage is 78.04%. Comparing base (95b7875) to head (e7d04ad).

Files with missing lines	Patch %	Lines
...tinations/google-enhanced-conversions/functions.ts	81.81%	2 Missing ⚠️
...ed-conversions/uploadConversionAdjustment/index.ts	81.81%	2 Missing ⚠️
...d-conversions/uploadConversionAdjustment2/index.ts	81.81%	2 Missing ⚠️
...kages/destination-actions/src/lib/hashing-utils.ts	77.77%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2876      +/-   ##
==========================================
+ Coverage   77.86%   78.04%   +0.18%     
==========================================
  Files        1049     1049              
  Lines       19450    19410      -40     
  Branches     3814     3762      -52     
==========================================
+ Hits        15145    15149       +4     
+ Misses       2965     2962       -3     
+ Partials     1340     1299      -41     

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