[tooling] Add a new argument adjuster for deleting plugin related command line args

Summary:
Currently both clangd and clang-tidy makes use of this mechanism so
putting it into tooling so that all tools can make use of it.

Reviewers: ilya-biryukov, sammccall

Subscribers: ioeric, cfe-commits

Differential Revision: https://reviews.llvm.org/D56856

llvm-svn: 351531