Revert "[FuzzMutate] Split out FuzzerCLI library that doesn't depend on IR."

This reverts commit 1c5e85b3.

It broke a lot of bots with a link error:
https://lab.llvm.org/buildbot/#/builders/171/builds/14222
https://lab.llvm.org/buildbot/#/builders/188/builds/13748
https://lab.llvm.org/buildbot/#/builders/109/builds/38127