IpcOneShotServer::accept is blocking and has no non-blocking version

[pYtoner]

A non-blocking version is needed to be used in an async context.
Something like IpcOneShotServer::try_accept()

If you think this is not too difficult for someone, who is very new to this lib, to implement this then I would happily do it.

What return type would make sense?

[tevoinea]

I'd like a non-blocking accept as well. What I was thinking was:

1. Create a try_accept in OsIpcOneShotServer that calls try_recv on the OsIpcReceiver
2. Create try_accept in IpcOneShotServer that uses the newly created try_accept from step 1

Return types shouldn't need to change since they already return Result.

I'm also happy to open a PR for this if the maintainers will accept the contribution!

[jdm]

I'd review a PR that added that implementation if you verify that it works as expected!