Revamp the "[clangd] Format tweak's replacements"

Summary:
This patch contains two parts:

1) reverts commit r353306.
2) move the format logic out from tweaks, keep tweaks API unchanged.

Reviewers: sammccall, ilya-biryukov

Reviewed By: ilya-biryukov

Subscribers: ilya-biryukov, ioeric, MaskRay, jkorous, arphaman, kadircet, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D58051

llvm-svn: 353712