Only the innermost exception is returned when activity functions throw

When an activity function throws an exception, we return a FailureDetails but it only represents the innermost exception. Request changing this behavior to match the other durable language implementations returning the outermost user error and all inner errors recursively.

Repro code:

    @FunctionName("CustomRetryActivityFunction")
    public String customRetryActivityFunction(
            @DurableOrchestrationTrigger(name = "ctx") TaskOrchestrationContext ctx) {
        TaskOptions options = new TaskOptions(retryContext -> {
            FailureDetails lastFailure = retryContext.getLastFailure();
            if (lastFailure != null
                    // BUG: Only the innermost failure is available in the Java SDK
                    // BUG: isCausedBy() relies on Class.forName() but we do not provide the fully qualified class name
                    //      in the FailureDetails 
                    && lastFailure.getErrorType().equals("OverflowException")
                    // && lastFailure.isCausedBy(InvalidOperationException.class)
                    // BUG: We do not implement inner failures in the Java SDK yet
                    // && lastFailure.getInnerFailure() != null
                    // && lastFailure.getInnerFailure().isCausedBy("java.lang.OverflowException")
                    && retryContext.getLastAttemptNumber() < 3) {
                return true;
            }
            return false;
        });
        return ctx.callActivity("RaiseComplexException", ctx.getInstanceId(), options, String.class).await();
    }

    @FunctionName("RaiseComplexException")
    public String raiseComplexException(
            @DurableActivityTrigger(name = "instanceId") String instanceId,
            final ExecutionContext context) throws InvalidOperationException {
        AtomicInteger count = globalRetryCount.computeIfAbsent(instanceId, k -> new AtomicInteger(0));
        int current = count.incrementAndGet();
        if (current == 1) {
            OverflowException inner = new OverflowException("Inner exception message");
            InvalidOperationException ex = new InvalidOperationException(
                "This activity failed\r\nMore information about the failure", inner);
            throw ex;
        } else {
            return "Success";
        }
    }

Result:

首先追蹤 activity-function 失敗時回傳的 FailureDetails，以及 retryContext.getLastFailure() 如何公開這些資訊。將 Java SDK 的行為與 issue 中提到的其他 Durable 語言實作進行比較。當最外層的使用者錯誤、其完整限定型別，以及所有巢狀的內部錯誤都可以遞迴檢查時，即視為完成。