test(storage): workaround MSVC limits

[coryan]

I have a different version of MSVC compared to the version used in CI.
The tests do not compile without /bigobj, and presumably this affects
customers too. We probably should enable that option for all tests.

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This change is 

[google-cloud-cpp-bot]

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[codecov]

Codecov Report

Merging #8357 (291d011) into main (5f0c674) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #8357   +/-   ##
=======================================
  Coverage   94.98%   94.99%           
=======================================
  Files        1360     1360           
  Lines      121062   121062           
=======================================
+ Hits       114996   114997    +1     
+ Misses       6066     6065    -1     

Impacted Files	Coverage Δ
google/cloud/bigtable/internal/common_client.h	94.02% <0.00%> (-5.98%)	⬇️
...integration_tests/schema_admin_integration_test.cc	98.88% <0.00%> (-1.12%)	⬇️
google/cloud/completion_queue_test.cc	97.14% <0.00%> (+0.19%)	⬆️
...cloud/pubsub/internal/subscription_session_test.cc	98.25% <0.00%> (+0.49%)	⬆️
...le/cloud/internal/default_completion_queue_impl.cc	97.72% <0.00%> (+0.56%)	⬆️
...ud/spanner/integration_tests/client_stress_test.cc	86.18% <0.00%> (+0.65%)	⬆️
google/cloud/pubsub/subscriber_connection_test.cc	97.91% <0.00%> (+0.69%)	⬆️

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