[clangd] Log all ignored diagnostics.

Summary:
To aid debugging failures and crashes.
Only part of ignored diagnostics was logged before, now we log all of
them.

Reviewers: ioeric, hokein, sammccall

Reviewed By: hokein

Subscribers: klimek, jkorous-apple, cfe-commits

Differential Revision: https://reviews.llvm.org/D43123

llvm-svn: 324888