[PM] Remove the 'AnalysisManagerT' type parameter from numerous layers

[PM] Remove the 'AnalysisManagerT' type parameter from numerous layers
of templates in the new pass manager.

The analysis manager is now itself just a template predicated on the IR
unit. This makes lots of the templates really trivial and more clear:
they are all parameterized on a single type, the IR unit's type.
Everything else is a function of that. To me, this is a really nice
cleanup of the APIs and removes a layer of 'magic' and 'indirection'
that really wasn't there and just got in the way of understanding what
is going on here.

llvm-svn: 225784