tools/tests: Drop obsolete mce-test infrastructure

tools/tests: Drop obsolete mce-test infrastructure

mce-test has a test suite, but it depends on xend, needs to run in-tree, and
requires manual setup of at least one guest, and manual parameters to pass
into cases.  Drop the test infrasturcture.

Move the one useful remaining item, xen-mceinj, into misc/, fixing some minor
style issues as it goes.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>