feat: alias single anyOf/allOf types

[perher]

This PR adds optional support for "inlining" or "collapsing" a subtype when it declares a single subschema of anyOf/allOf type. When feature is enabled in config and all conditions are fulfilled (no extra properties should be defined) then an alias type is created instead of declaring a duplicate type.

There is always a a maintenance burden of supporting optional features, I think it is worth it in this case since overhead is quite small.

fixes #296

extracted from #473

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Codecov Report

❌ Patch coverage is 77.77778% with 4 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@37d54f2). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
pkg/generator/schema_generator.go	75.00%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #509   +/-   ##
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  Coverage        ?   41.20%           
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  Files           ?       66           
  Lines           ?     5662           
  Branches        ?        0           
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  Hits            ?     2333           
  Misses          ?     3050           
  Partials        ?      279           

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