[PM] In the PassManager template, remove a pointless indirection through

[PM] In the PassManager template, remove a pointless indirection through
a nested class template for the PassModel, and use the T-suffix for the
two typedefs to match the code in the AnalysisManager.

This is the last of the fairly fundamental code cleanups here. Will be
focusing on the printing of analyses next to finish that aspect off.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225785 91177308-0d34-0410-b5e6-96231b3b80d8