Replace std::copy with a back inserter with vector append where feasible

Replace std::copy with a back inserter with vector append where feasible

All of the cases were just appending from random access iterators to a
vector. Using insert/append can grow the vector to the perfect size
directly and moves the growing out of the loop. No intended functionalty
change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230845 91177308-0d34-0410-b5e6-96231b3b80d8