[BUG] Rust wasm32-unknown-unknown build is broken with 7.15.0

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

The new async file stream support for reqwest client breaks the WASM build.

• supportAsync=true (default) implies vendorExtensions.useAsyncFileStream=true, it will add tokio as a dependency with features incompatible with WASM
• supportAsync=false, it will enable the blocking feature of reqwest, which does not build for WASM

error: Only features sync,macros,io-util,rt,time are supported on wasm.
   --> /home/jmlx/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.47.1/src/lib.rs:475:1
    |
475 | compile_error!("Only features sync,macros,io-util,rt,time are supported on wasm.");
    |

So IMHO, essentially, the WASM build is essentially 100% broken on 7.15.0.

openapi-generator version

7.15.0

OpenAPI declaration file content or url

swagger: "2.0"
info:
  title: File Streaming Test API
  version: 1.0.0

paths:
    /upload:
      post:
        consumes:
            - application/octet-stream
        description: Upload a file from the local filesystem
        operationId: uploadFile
        parameters:
          - description: A test file
            in: body
            name: inputStream
            schema:
              format: binary
              type: string
        responses:
          '200':
            description: Success

Generation Details

java ${JAVA_OPTS} -jar ${CODEGEN} generate -i \"${INPUT_FILE}\" \
        -g ${lang} \
        -o ${TMP_PATH} \
        --additional-properties=packageName=gltf_live_client_sdk \
        --additional-properties=publishRustRegistry=false \
        --additional-properties=library=reqwest \
        --additional-properties=avoidBoxedModels=true

Steps to reproduce

1. Generate the Rust client code
2. Attempt to build for wasm32-unknown-unknown

Related issues/PRs

https://github.com/OpenAPITools/openapi-generator/pull/21771

Suggest a fix

useAsyncFileStream should be a Cargo feature

Start by reproducing the generated Rust reqwest client build for wasm32-unknown-unknown using the OpenAPI declaration and generation details in the issue. Review related PR 21771 and the handling of supportAsync and vendorExtensions.useAsyncFileStream; done means the generated client builds for WASM without incompatible tokio or reqwest blocking features, with useAsyncFileStream controlled as a Cargo feature.