Parser: Don't manage TemplateAnnotationIds in a delayed cleanup pool.

Parser: Don't manage TemplateAnnotationIds in a delayed cleanup pool.

Instead, make it the allocation function's responsibility to add them
to a list and clear it when a top-level decl is finished.

This plugs leakage of TemplateAnnotationIds. DelayedCleanupPool is
ugly and unused, remove it.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@154743 91177308-0d34-0410-b5e6-96231b3b80d8