feat(GCS+gRPC): implement BucketAccessControl parser

[coryan]

Fixes #4174

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This change is 

[google-cloud-cpp-bot]

Google Cloud Build Logs
For commit: dc13c430f5bff9788e23a36a1b749bce8d7b31f4

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[codecov]

Codecov Report

Merging #7763 (dc13c43) into main (b2fe267) will decrease coverage by 0.00%.
The diff coverage is 96.66%.

@@            Coverage Diff             @@
##             main    #7763      +/-   ##
==========================================
- Coverage   95.15%   95.15%   -0.01%     
==========================================
  Files        1271     1273       +2     
  Lines      114633   114693      +60     
==========================================
+ Hits       109079   109136      +57     
- Misses       5554     5557       +3     

Impacted Files	Coverage Δ
google/cloud/storage/bucket_access_control.h	100.00% <ø> (ø)
...gle/cloud/storage/internal/access_control_common.h	100.00% <ø> (ø)
...rage/internal/grpc_bucket_access_control_parser.cc	93.75% <93.75%> (ø)
...internal/grpc_bucket_access_control_parser_test.cc	100.00% <100.00%> (ø)
...le/cloud/storage/internal/curl_download_request.cc	88.69% <0.00%> (-1.07%)	⬇️
...sub/internal/batching_publisher_connection_test.cc	99.60% <0.00%> (+0.19%)	⬆️
...ud/spanner/integration_tests/client_stress_test.cc	86.18% <0.00%> (+0.65%)	⬆️

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