[Test Gap][mux simulator][dualtor] Need testcase to validate mux_simulator could handle/close timeout requests

[lolyu]

Test Gap Description

The mux_simulator was not able to close CLOSE_WAIT connections, leads to a socket fd leak and listen overflow.
Please check #16495 for more details.

We need a testcase to validate this.

Test Plan

1. flooding timeout requests to mux_simulator.
2. check the mux_simulator accept queue, ensure no listen overflow.
3. send a toggle request to mux_simulator and the request is handled properly.

Test environment

No response

Attach files (if any)

No response

[yxieca]

@lolyu is this issue fixed by your PR already?

[lolyu]

@lolyu is this issue fixed by your PR already?

Hi @yxieca, yes, this test gap is to add an infra stress test to cover this scenario.