feat(rust): allow more granular Rust integer types and cleaned up clippy warnings

[thrykol]

• Added CLI option to down cast integers to their best fit
  • Will only occur when minimum and maximum are both set
  • Configuration defaults to false
• Added CLI option to prefer unsigned integers
  • Will only occur when minimum is defined and non-negative
  • Configuration defaults to false
• toParamName now lower cases to adhere to rustfmt
  • Previously, the tail component of $ref was being upper cased
• Added unit tests around all new features

@frol
@farcaller
@richardwhiuk
@paladinzh

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package 
  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh
  

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[wing328]

LGTM. Thanks for the enhancement.

[spacether]

Sample up to date test failed in CI for this PR

[spacether]

I am fixing it in:
#12817

[wing328]

This result in change of variable name (e.g. pet_id => petid): https://github.com/OpenAPITools/openapi-generator/pull/12817/files

I'll file a PR to fix it by remove https://github.com/OpenAPITools/openapi-generator/pull/12479/files#diff-8daa2cc862ff0a63dd72dac551951b1bb07675e3cc0609a6dea55d2e85492520R440 instead.

[wing328]

Filed #12820

[wing328]

Thanks @spacether