Tooling: When applying a set of replacements, do deletions before

Tooling: When applying a set of replacements, do deletions before
insertions. It is unlikely to be the intention to delete parts of newly
inserted code. To do so, changed sorting Replacements at the same offset
to have decreasing length.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@239809 91177308-0d34-0410-b5e6-96231b3b80d8