Configure idempotent upload to Google Cloud Storage

[vpaturet]

Summary

The goal of this PR is to prevent failure to upload graph building artifacts to Google Cloud Storage due to transient network issues/ server errors as described in issue #4268
By default the Google Storage client library does not retry failed upload operations.
See https://cloud.google.com/storage/docs/retry-strategy#java for more details about which operations are retried by default.
To activate retry on error, it is necessary to make the operation "conditionally idempotent" by detecting concurrent update:

• if the blob already exists in the target bucket and must be updated: check that the blob version ("generation") did not change between the beginning and the end of the upload operation.
• if the blob does not exist yet in the target bucket and must be created: check that the blob still does not exist when the upload operation completes.

Expected behavior: if a transient network issue/server error prevents an upload operation to complete, it will be retried with the default retry settings: 6 attempts, exponential backoff factor: 2, initial delay: 1s
(See https://cloud.google.com/storage/docs/retry-strategy#client-libraries for details on the default retry settings)

Side effect: if another process concurrently updates the blob, the upload process will fail.

Issue

closes #4268

Unit tests

✅

Documentation

No

[codecov-commenter]

Codecov Report

Merging #4269 (608c7d1) into dev-2.x (c14f86b) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@              Coverage Diff              @@
##             dev-2.x    #4269      +/-   ##
=============================================
- Coverage      56.89%   56.87%   -0.02%     
+ Complexity     10586    10583       -3     
=============================================
  Files           1402     1402              
  Lines          57170    57170              
  Branches        6603     6603              
=============================================
- Hits           32526    32518       -8     
- Misses         22630    22638       +8     
  Partials        2014     2014              

Impacted Files	Coverage Δ
...tripplanner/ext/datastore/gs/GsFileDataSource.java	0.00% <0.00%> (ø)
...pplanner/ext/datastore/gs/GsOutFileDataSource.java	0.00% <0.00%> (ø)
...ph_builder/module/ned/MissingElevationHandler.java	93.70% <0.00%> (-1.58%)	⬇️
...pplanner/graph_builder/module/osm/OSMDatabase.java	76.47% <0.00%> (-0.95%)	⬇️
...lanner/routing/vehicle_parking/VehicleParking.java	82.03% <0.00%> (-0.79%)	⬇️

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[leonardehrenfried]

Since this is a sandbox feature, we can merge that in with one approval, preferably by someone at Entur.