refactor: a handful more versioned clients

[dbolduc]

Part of the work for #10170

• retail
• run
• scheduler
• secretmanager
• securitycenter

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This change is 

[codecov]

Codecov Report

Base: 93.65% // Head: 93.64% // Decreases project coverage by -0.01% ⚠️

Coverage data is based on head (815142f) compared to base (8640260).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10932      +/-   ##
==========================================
- Coverage   93.65%   93.64%   -0.01%     
==========================================
  Files        1717     1717              
  Lines      154933   154933              
==========================================
- Hits       145097   145092       -5     
- Misses       9836     9841       +5     

Impacted Files	Coverage Δ
google/cloud/internal/async_connection_ready.cc	89.36% <0.00%> (-4.26%)	⬇️
...e/cloud/pubsublite/internal/alarm_registry_impl.cc	97.05% <0.00%> (-2.95%)	⬇️
google/cloud/pubsub/subscriber_connection_test.cc	98.78% <0.00%> (-1.22%)	⬇️
google/cloud/internal/curl_wrappers.cc	94.18% <0.00%> (-1.17%)	⬇️
...cloud/pubsub/internal/subscription_session_test.cc	97.99% <0.00%> (-0.51%)	⬇️
...le/cloud/storage/internal/curl_download_request.cc	88.62% <0.00%> (-0.34%)	⬇️
google/cloud/pubsub/samples/samples.cc	87.01% <0.00%> (+0.07%)	⬆️
google/cloud/storage/parallel_upload.cc	98.62% <0.00%> (+0.34%)	⬆️
...bigtable/examples/bigtable_hello_instance_admin.cc	83.00% <0.00%> (+2.00%)	⬆️

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