Only the innermost exception is returned when activity functions throw

首先跟踪 activity-function 失败时返回的 FailureDetails，以及 retryContext.getLastFailure() 如何暴露这些信息。将 Java SDK 的行为与 issue 中提到的其他 Durable 语言实现进行比较。当最外层的用户错误、其完全限定类型以及所有嵌套的内部错误都可以递归检查时，即视为完成。

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: