Fix & improves

[Coldwings]

Bug fix:

• photon gdb tool script fits current register on stack layout
• fix unit test designed not fit for mutex lock that may perform thread_yield spin
• http client dialer leaks tcp_socket_client

Feature:

• new AsyncAwaiter for Executor and WorkPool implementation

[beef9999]

此处是用future promise代替了原来的cond variable嘛？ future promise性能怎么样，最终会被实现成啥同步原语？

[Coldwings]

GCC的标准库（libstdc++）中，future的wait动作使用condition_variable的wait_for实现。