[lit] Split TestingConfig.frompath() into separate ctor and load methods.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188038 91177308-0d34-0410-b5e6-96231b3b80d8
[lit] Inject the lit specific config object as 'lit_config' when loading config files.

 - Injecting it as 'lit' is gross, since that name should be used to refer to
   the actual package. For now both are available so it is possibly to cleanup
   test config files incrementally.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188039 91177308-0d34-0410-b5e6-96231b3b80d8
[lit] Rename lit.{TestFormats,Util} to their aliased names {formats,util}.

 - With compatibility hack in lit.__init__, so this hopefully shouldn't break
   anything.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188040 91177308-0d34-0410-b5e6-96231b3b80d8