Result proxy should be required for both workflows (TEE, non TEE)

[zguesmi]

The worker should not use implicit values for the result-proxy url when uploading a non TEE result. The workflow should be as similar as possible to TEE. This would make it easier for the SDK.

iexec-worker/src/main/java/com/iexec/worker/result/ResultService.java

Line 153 in 61c8d21

public String uploadResultAndGetLink(String chainTaskId) {