Use Operations.Send over SendHelper

[JR-Morgan]

in specklesystems/speckle-sharp-sdk#68, We updated Operations.Send to return the required references.
In this PR, I've updated connectors to use this instead of the older SendHelper

We may decide later to bring back a Sender service instead of using statics, but we need to plan this as a larger restructure of our Sdks.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 8.31%. Comparing base (db60e3e) to head (72da82b).

Files	Patch %	Lines
...le.Connectors.Utils/Operations/RootObjectSender.cs	0.00%	2 Missing ⚠️
...onnectors.Utils/Caching/NullSendConversionCache.cs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             dev    #140      +/-   ##
========================================
+ Coverage   8.19%   8.31%   +0.11%     
========================================
  Files        233     232       -1     
  Lines       4391    4332      -59     
  Branches     503     491      -12     
========================================
  Hits         360     360              
+ Misses      4021    3962      -59     
  Partials      10      10              

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