Reland "[clangd] Migrate last tweak tests to TweakTesting.h and remove old helpers. NFC"

This reverts commit 3dcf55aa45bad800533b36b70a14ebeb2b84e219, and avoids
use of multiline raw strings in macro calls.

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@370304 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed