fix: rename BoundModelBase to BaseBoundModel

[jooola]

Use a consistent name pattern for base classes.

[codecov]

Codecov Report

❌ Patch coverage is 95.12195% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.95%. Comparing base (8f0572e) to head (66c7f0d).

Files with missing lines	Patch %	Lines
hcloud/core/client.py	66.66%	2 Missing ⚠️

Additional details and impacted files

@@                           Coverage Diff                            @@
##           refactor-rename-resource-base-client     #533      +/-   ##
========================================================================
- Coverage                                 96.01%   95.95%   -0.07%     
========================================================================
  Files                                        64       64              
  Lines                                      2938     2942       +4     
========================================================================
+ Hits                                       2821     2823       +2     
- Misses                                      117      119       +2     

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