Ensure log buffers are dumped to file on uncaught exceptions

Move the functionality for wrapping an uncaught exception pre-handler
from PluginManager to a standalone manager. Make DumpHandler register
another uncaught exception pre-handler that will tell the log buffer
eulogizer to dump contents to a file.

Fixes: 213884413
Test: manually verified, added tests, and ran atest
Change-Id: If829fc33769819624530f766178689ecf0374926