Factor out attributes into EventAttributes class

[cortadocodes]

Contents (#721)

Enhancements

• Remove need to (de)serialise None attribute values

Refactoring

• Factor out event attributes into EventAttributes class

Operations

• Revert change to workload identity provider for test runner

Other

• Disable question cancellation methods for now

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 97.72727% with 2 lines in your changes missing coverage. Please review.

Please upload report for BASE (rc-kueue@fd6289d). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
octue/cloud/pub_sub/service.py	93.93%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             rc-kueue     #721   +/-   ##
===========================================
  Coverage            ?   93.69%           
===========================================
  Files               ?       85           
  Lines               ?     3682           
  Branches            ?        0           
===========================================
  Hits                ?     3450           
  Misses              ?      232           
  Partials            ?        0           

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