In this commit, we modify the set of default signals we attempt to catch in
order to execute a graceful shutdown. Before this commit, we would attempt
to catch/register for `SIGSTOP`. There're two issues with this
1. `SIGSTOP` is meant to be used in combination with `SIGCONCT` to allow a
process to be paused/resumed. Therefore, our action of shutting down once
received was incorrect.
2. `SIGSTOP` doesn't exist on windows, so users aren't able to compile on
this platform without modifying the codebase.
In this commit, we modify the primary `signal` package to instead catch
all signals. Before this commit, it would only catch the interrupt
signal sent from the kernel. With this new commit, we'll now also catch
(or attempt to catch): `SIGABRT`, `SIGTERM`, `SIGSTOP`, and `SIGQUIT`.
