feature: Implement basic support for record fields

[aiven-anton]

Issues to be discussed:

• This does not enable the Java compatibility tests for entities with records.
  These are currently failing as Hypothesis generates random bytes for the records fields. We should most likely introduce a RecordsBytes type and teach Hypothesis to generate some static record batch for this to begin with (no need to have more intricate knowledge of record batches yet).
• Java compatibility tests are failing when record batch fields are None. Why?
• It's probably fine to merge the integration test with @xfail. It needs to be solved at some point, but merging it doesn't make the current situation any worse.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (07553df) 96.86% compared to head (aa44fe7) 96.85%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #122      +/-   ##
==========================================
- Coverage   96.86%   96.85%   -0.02%     
==========================================
  Files          14       14              
  Lines        1022     1018       -4     
  Branches      142      140       -2     
==========================================
- Hits          990      986       -4     
  Misses         28       28              
  Partials        4        4              

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