feat: Add net xmit status cb for application can block to get it

[xcguang]

Describe the PR

Current poll mode speed down net throughput, we can add a api for xmitting status cb, application can be blocked to wait usb idle.

[xcguang]

@hathach Hello, could you consider of this PR?

[hathach]

thank for the PR, I am currently busy with other works, I will try to review this as soon as possible. Please be patient