This commit significantly refactors the alsa backend's `EventLoop::run`
implementation in order to allow for better error handling throughout
the loop. This removes many cases that would previously `panic!` in
favour of calling the user callback with the necessary error and
removing the corrupt stream. Seeing as the method cannot return, a
catch-all `panic!` still exists at the end of the method, however this
refactor should make it much easier to remove this restriction in the
future.
e41baa248b