[Bug]: http-client-java, unbranded, response as wired type Base64, Base64Uri

[weidongxu-microsoft]

Describe the bug

azure supports this in RestProxy as

        @ReturnValueWireType(Base64Url.class)
        Mono<Response<List<byte[]>>> getBase64Url(@HostParam("$host") String host, @HeaderParam("Accept") String accept,
            Context context);

@ReturnValueWireType would handle the de-serialization.

---

In clientcore, Base64Uri would work after we add returnValueWireType = Base64Uri.class.

However, byte[] with Base64 encode is not handled.

Reproduction

http-specs test

Checklist

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