[obj2yaml][yaml2obj]Locate all .yaml and .test tests

A number of the obj2yaml tests end in .yaml, but .yaml is not a default
file type picked up by lit, so these tests weren't being run when
running the testsuite as a whole (they could be run explicitly still).
This change adds a lit local config file to specify the known file types
for obj2yaml tests (.yaml and .test). Additionally, it fixes the
yaml2obj config file to allow both .test and .yaml suffixed tests
(previously, the two tests ending in '.test' were not being run).

Reviewed by: grimar

Differential Revision: https://reviews.llvm.org/D58439

llvm-svn: 354474