WIP: Support transaction in the docstore

[sandeepvinayak]

docstore/all

Details in the issue : https://github.com/google/go-cloud/issues/3501

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[sandeepvinayak]

@eliben @vangent We are trying to add the transactions support/atomic writes in the docstore and this is the high level idea of how can we support that in go-cloud. https://docs.google.com/document/d/1UVj1kmwDfrs5qm8r7X1p4fAFmsdPEeBHcvWJ8zWF1dY/edit?tab=t.0

The PR is just at a high level to support the idea. Let me know what you think about it and we can help to drive it further.

[sandeepvinayak]

@jba thanks for your feedback, I addressed all of the comments, please take another look

[sandeepvinayak]

@jba, I addressed your latest 2 comments

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 71.79487% with 11 lines in your changes missing coverage. Please review.

Project coverage is 73.28%. Comparing base (61f69d3) to head (8d0616d). Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
docstore/awsdynamodb/dynamo.go	46.66%	8 Missing :warning:
docstore/docstore.go	75.00%	3 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3500      +/-   ##
==========================================
+ Coverage   73.26%   73.28%   +0.01%     
==========================================
  Files         113      113              
  Lines       15065    15080      +15     
==========================================
+ Hits        11038    11051      +13     
- Misses       3261     3263       +2     
  Partials      766      766              

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[sandeepvinayak]

@jba the codecov report is under-reporting because the conformance tests are disabled for now but I verified the tests we added are good for dynamo. I will enable the 2 conformance tests added along with the other providers in the follow up PR.

[jba]

Thanks for the PR! Looking forward to the follow-ups.