[exec] Add stream api to improve exec ease of use

[ideal]

Hi all, the current use of java8 has been very extensive. I designed a
stream api based simplified `exec` and verified its usability in a lot of
scenarios. Share my api now.

demo:

        JVMLauncher<Integer> launcher = JVMLaunchers.<Integer>newJvm()
                .setCallable(() -> {
                    System.out.println("************ exec task jvm
start ***************");
                    TimeUnit.SECONDS.sleep(1);
                    System.out.println("************ exec task jvm
stop ***************");
                    return 1;
                })
                .setXms("16m")
                .setXmx("16m")
                .addUserjars(Collections.emptyList())
                .setConsole((msg) -> System.err.println(msg))
                .build();

        VmFuture<Integer> out = launcher.startAndGet();   --run