[Smart Hashing] update processhashing to handle undefined values

[harsh-joshi99]

Update the process hashing to handle undefined values since some destination might throw in case we send an empty string.
Also casted the response of process hashing to string wherever required.

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 25.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 78.35%. Comparing base (c741b70) to head (2ca2c2f).
Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
...kages/destination-actions/src/lib/hashing-utils.ts	0.00%	1 Missing and 1 partial ⚠️
...nations/linkedin-audiences/updateAudience/index.ts	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2811      +/-   ##
==========================================
- Coverage   78.36%   78.35%   -0.01%     
==========================================
  Files        1042     1042              
  Lines       18937    18939       +2     
  Branches     3646     3646              
==========================================
  Hits        14840    14840              
- Misses       2860     2861       +1     
- Partials     1237     1238       +1     

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