doc(common): use real Doxygen groups

[coryan]

This change is 

[codecov]

Codecov Report

Base: 93.97% // Head: 93.97% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (94c7e30) compared to base (79b0094).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #10504   +/-   ##
=======================================
  Coverage   93.97%   93.97%           
=======================================
  Files        1627     1627           
  Lines      146844   146844           
=======================================
+ Hits       138001   138002    +1     
+ Misses       8843     8842    -1     

Impacted Files	Coverage Δ
google/cloud/internal/async_retry_unary_rpc.h	96.49% <ø> (ø)
google/cloud/internal/retry_policy.h	100.00% <ø> (ø)
google/cloud/kms_key_name.h	80.00% <ø> (ø)
google/cloud/log.h	90.74% <ø> (ø)
google/cloud/polling_policy.h	100.00% <ø> (ø)
google/cloud/project.h	100.00% <ø> (ø)
google/cloud/status_or.h	100.00% <ø> (ø)
google/cloud/stream_range.h	100.00% <ø> (ø)
...bigtable/examples/bigtable_hello_instance_admin.cc	81.00% <0.00%> (-2.00%)	⬇️
...integration_tests/schema_admin_integration_test.cc	98.88% <0.00%> (-1.12%)	⬇️
... and 5 more

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