Add request interceptor API to RCTMultipartDataTask (#55916)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/55916

## Summary:
Replace the hardcoded `RCTDevSupportHttpHeaders` integration in `RCTMultipartDataTask` with a generic request interceptor API. This allows consumers to register a block via `RCTSetCustomMultipartDataTaskRequestInterceptor` that can inspect and modify multipart data task requests before they are sent, without coupling `RCTMultipartDataTask` to any specific header injection mechanism.

## Changelog:
[IOS][ADDED] - Add `RCTSetCustomMultipartDataTaskRequestInterceptor` API to allow custom modification of multipart data task requests before they are sent

Reviewed By: cortinico

Differential Revision: D95219954

fbshipit-source-id: 7752b2ee44ee9d4db574a9866661e1a717b75bed