unique_ptrify LLVMContextImpl::CAZConstants

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222714 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "unique_ptrify LLVMContextImpl::CAZConstants"

Missed the complexities of how these elements are destroyed.

This reverts commit r222714.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222715 91177308-0d34-0410-b5e6-96231b3b80d8