[BugFix] [Rust*] model-name-prefix causing invalid generated code

[linxGnu]

Kindly ping @wing328 to review.

This PR Fixes #19632

Integration test without problems:

./bin/generate-samples.sh bin/configs/manual/rust-axum-*
mvn integration-test -f samples/server/petstore/rust-axum/pom.xml

Noted: this PR update rust-axum samples properties to generate models with prefix.

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  ./bin/utils/export_docs_generators.sh
  

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  Commit all changed files.
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[GeorgeFkd]

Can you also generate the samples for the rest of the Rust implementations? As the change you did also affects all of the rust generators. Just do ./bin/generate-samples.sh ./bin/configs/*.yaml as indicated to be sure that all affected generators are properly generated and pass the checks.

[linxGnu]

@GeorgeFkd
Ran ./bin/generate-samples.sh ./bin/configs/*.yaml -> no changes -> safe

[linxGnu]

Added an sample for reqwest with model-name-prefix. PTAL @wing328
cc @GeorgeFkd as well to review