feat(common): retry loops signal via error info

[coryan]

Use the Status::error_info() to signal details about why a retry loop fails. We were using the contents of the message.

Fixes #12303

---

This change is 

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (449bf80) 93.49% compared to head (0e30221) 93.50%.
Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main   #12313    +/-   ##
========================================
  Coverage   93.49%   93.50%            
========================================
  Files        2014     2014            
  Lines      178020   178261   +241     
========================================
+ Hits       166441   166677   +236     
- Misses      11579    11584     +5     

Files Changed	Coverage Δ
google/cloud/internal/retry_loop_helpers.h	100.00% <ø> (ø)
google/cloud/status.h	100.00% <ø> (ø)
..._tests/tests/golden_thing_admin_connection_test.cc	99.59% <100.00%> (+<0.01%)	⬆️
...s/tests/golden_thing_admin_rest_connection_test.cc	99.60% <100.00%> (+<0.01%)	⬆️
google/cloud/internal/async_rest_retry_loop.h	100.00% <100.00%> (ø)
...oogle/cloud/internal/async_rest_retry_loop_test.cc	98.60% <100.00%> (-0.64%)	⬇️
google/cloud/internal/async_retry_loop.h	100.00% <100.00%> (ø)
google/cloud/internal/async_retry_loop_test.cc	98.85% <100.00%> (-0.65%)	⬇️
google/cloud/internal/rest_retry_loop.h	100.00% <100.00%> (ø)
google/cloud/internal/rest_retry_loop_test.cc	97.48% <100.00%> (+0.18%)	⬆️
... and 9 more

... and 5 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.