[PM] Change the name of the repeating utility to something less

[PM] Change the name of the repeating utility to something less
overloaded (and simpler).

Sean rightly pointed out in code review that we've started using
"wrapper pass" as a specific part of the old pass manager, and in fact
it is more applicable there. Here, we really have a pass *template* to
build a repeated pass, so call it that.

llvm-svn: 277689