test infra: move test event-related handling into its own package

test infra: move test event-related handling into its own package

This change moves all the test event handling and its related
ResultsFormatter classes out of the packages/Python/lldbsuite/test dir
into a packages/Python/lldbsuite/test_event package. Formatters are
moved into a sub-package under that.

I am limiting the scope of this change to just the motion and a few
minor issues caught by a static Python checker (e.g. removing unused
import statements).

This is a pre-step for adding package-level tests to the test event
system. I also intend to simplify test event results formatter selection
after I make sure this doesn't break anybody.

See:
http://reviews.llvm.org/D19288

Reviewed by:
Pavel Labath

llvm-svn: 266885