Implement Group sync for KeeShare

[droidmonkey]

Originally contributed through #9778, code provided by @evur

Fixes #3045

Screenshots

Testing strategy

Type of change

• ✅ Bug fix (non-breaking change that fixes an issue)
• ✅ New feature (change that adds functionality)

[codecov]

Codecov Report

Attention: Patch coverage is 20.51282% with 31 lines in your changes missing coverage. Please review.

Project coverage is 63.82%. Comparing base (fb022cb) to head (64feaa8).

Files with missing lines	Patch %	Lines
src/keeshare/ShareExport.cpp	0.00%	25 Missing ⚠️
src/keeshare/group/EditGroupWidgetKeeShare.cpp	33.33%	6 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #11593      +/-   ##
===========================================
- Coverage    63.87%   63.82%   -0.06%     
===========================================
  Files          362      362              
  Lines        38170    38199      +29     
===========================================
- Hits         24380    24377       -3     
- Misses       13790    13822      +32     

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[droidmonkey]

I fixed up the code, but this does break existing behavior since recursing is off by default. Need to think about whether to send this out with 2.7.10 or not.