[PassManager] Ensure destructors of cached AnalysisUsage objects are run

[PassManager] Ensure destructors of cached AnalysisUsage objects are run

In 254760, I introduced the usage of a BumpPtrAllocator for the AnalysisUsage instances held by the PassManger.  This turns out to have been incorrect since a BumpPtrAllocator does not run the destructors of objects when deallocating memory.  Since a few of our SmallVector's had grown beyond their small size, we end up with some leaked memory.  We need to use a SpecificBumpPtrAllocator instead.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@254803 91177308-0d34-0410-b5e6-96231b3b80d8