`restart=True` is never passed to `provisioner.terminate`

[caenrigen]

Hi, I am working on a provisioner for remote kernels via SSH (https://github.com/caenrigen/sshpyk/tree/provisioner).

I noticed that my provisioner's async def terminate(self, restart: bool = False) never receives a restart=True value even if I restart the kernel (in JupyterLab).

From inspecting jupyter_client this happens because async def _async_send_kernel_sigterm(self, restart: bool = False) is never being passed the restart argument at all (and it defaults always to False from default python args):

jupyter_client/jupyter_client/manager.py

Line 480 in 6ea834d

await self._async_send_kernel_sigterm()

Is this a bug or intended behaviour? Would you accept a PR if it is a bug? though I probably have to implement a workaround anyway for some backwards compatibility with previous version of jupyter_client, I think I should be able to by caching the restart argument passed to provisioner.shutdown_requested.

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As a side note I also notice that _async_kill_kernel does not always receive the argument either, intended?

jupyter_client/jupyter_client/manager.py

Line 545 in 6ea834d

await self._async_kill_kernel()