Allow usage of other multipart types in Reactive REST Client

[geoand]

Fixes: #28026

[quarkus-bot]

Failing Jobs - Building 55e4353

Status	Name	Step	Failures	Logs	Raw logs
✔️	JVM Tests - JDK 11
✔️	JVM Tests - JDK 17
✖	JVM Tests - JDK 17 Windows	Build	Failures	Logs	Raw logs
✔️	JVM Tests - JDK 19

Full information is available in the Build summary check run.

Failures

⚙️ JVM Tests - JDK 17 Windows #

- Failing: extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment 
! Skipped: extensions/keycloak-admin-client-reactive/deployment extensions/oidc-client-reactive-filter/deployment extensions/oidc-token-propagation-reactive/deployment and 25 more

📦 extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment

✖ io.quarkus.resteasy.reactive.server.test.CloserTest.test line 102 - More details - Source on GitHub

java.lang.AssertionError: 
1 expectation failed.
Response body doesn't match expectation.