fix(datastore): handle not found errors from azure, s3 and gcs

[corrieriluca]

For some storage backend implementations, "not found" errors were not implemented for Get and Check operations resulting in unwanted 500 error from the Datastore API.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 0% with 62 lines in your changes missing coverage. Please review.

Project coverage is 43.81%. Comparing base (cb02ead) to head (3579db3).

Files with missing lines	Patch %	Lines
internal/datastore/storage/gcs/gcs.go	0.00%	34 Missing ⚠️
internal/datastore/storage/s3/s3.go	0.00%	22 Missing ⚠️
internal/datastore/storage/azure/azure.go	0.00%	6 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #511      +/-   ##
==========================================
- Coverage   44.24%   43.81%   -0.43%     
==========================================
  Files          78       78              
  Lines        5517     5571      +54     
==========================================
  Hits         2441     2441              
- Misses       2868     2922      +54     
  Partials      208      208              

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