Function to convert controlpb.folder attributes to gcs.Folder

[Tulsishah]

Description

• Function to convert controlpb.folder attribute to gcs.Folder as it will required in many places.
• In HNS, folder paths returned by control client APIs are in the form of: projects/_/buckets/{bucket}/folders/{folder}
  Introduced method extracts the folder name from such a string.
  e.g.
  control client GetFolder(folder1/folder2) returns folder Name as projects/_/buckets/{bucket}/folders/folder1/folder2
  We will fetch folder1/folder2 from response and set it in folder attribute.

Link to the issue in case of a bug fix.

NA

Testing details

1. Manual - NA
2. Unit tests - Added
3. Integration tests - Automated

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.95%. Comparing base (f788ddd) to head (dfd24be).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2139      +/-   ##
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+ Coverage   71.93%   71.95%   +0.01%     
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  Files         101      102       +1     
  Lines       11125    11131       +6     
==========================================
+ Hits         8003     8009       +6     
  Misses       2792     2792              
  Partials      330      330              

Flag	Coverage Δ
unittests	71.95% <100.00%> (+0.01%)	⬆️

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[charith87]

I've only added nit comments. So approving the review.