Add an "interrupt timeout" to Process, and pipe that through the

ProcessGDBRemote plugin layers.

Also fix a bug where if we tried to interrupt, but the ReadPacket
wakeup timer woke us up just after the timeout, we would break out
the switch, but then since we immediately check if the response is
empty & fail if it is, we could end up actually only giving a
small interval to the interrupt.

Differential Revision: https://reviews.llvm.org/D102085