DebugInfo: Introduce DIBuilder::replaceTemporary()

DebugInfo: Introduce DIBuilder::replaceTemporary()

Add `DIBuilder::replaceTemporary()` as a replacement for
`DIDescriptor::replaceAllUsesWith()`.  I'll update clang to use the new
method, and then come back to delete the original.

This method dispatches to `replaceAllUsesWith()` or
`replaceWithUniqued()`, depending on whether the replacement is actually
a different node from the original.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234695 91177308-0d34-0410-b5e6-96231b3b80d8