feat(storage): release *StallMinimumThroughputOption

[coryan]

These options have proven useful. Time to move them out of storage_experimental.

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This change is 

[google-cloud-cpp-bot]

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For commit: 38055d8f5391c8ed0a3f53284a4bd2bbefea9a21

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[dbolduc]

I think this is a feat(storage): release *StallMinimumThroughputOption

[codecov]

Codecov Report

Merging #9813 (38055d8) into main (eb5ad36) will decrease coverage by 0.00%.
The diff coverage is 86.66%.

@@            Coverage Diff             @@
##             main    #9813      +/-   ##
==========================================
- Coverage   94.24%   94.24%   -0.01%     
==========================================
  Files        1495     1495              
  Lines      139805   139801       -4     
==========================================
- Hits       131756   131749       -7     
- Misses       8049     8052       +3     

Impacted Files	Coverage Δ
google/cloud/storage/benchmarks/benchmark_utils.cc	26.21% <0.00%> (ø)
...enchmarks/aggregate_download_throughput_options.cc	85.32% <100.00%> (ø)
...arks/aggregate_download_throughput_options_test.cc	100.00% <100.00%> (ø)
.../benchmarks/aggregate_upload_throughput_options.cc	81.66% <100.00%> (ø)
...hmarks/aggregate_upload_throughput_options_test.cc	100.00% <100.00%> (ø)
...gle/cloud/storage/benchmarks/throughput_options.cc	84.91% <100.00%> (ø)
...loud/storage/benchmarks/throughput_options_test.cc	100.00% <100.00%> (ø)
google/cloud/storage/client_options.cc	88.46% <100.00%> (ø)
google/cloud/storage/client_options_test.cc	100.00% <100.00%> (ø)
...gle/cloud/storage/internal/curl_request_builder.cc	91.91% <100.00%> (-0.17%)	⬇️
... and 7 more

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