[clangd] Extend --check to time clang-tidy checks, so we can block slow ones

misc-const-correctness is so catastrophically slow that we need to block it
from running. But we need a way to detect this without breaking users first.

This is part of a plan to run only fast checks by default.
More details in  https://github.com/clangd/clangd/issues/1337

Differential Revision: https://reviews.llvm.org/D136082