[clangd] log request/response messages with method/ID/error at INFO level

Summary: Bodies are logged at VERBOSE level (since r336785), tweak the formatting.

Reviewers: hokein

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

Differential Revision: https://reviews.llvm.org/D49224

llvm-svn: 336899