This CL implements the first set of diagnostic notifications.
When Torque compilation fails, the language server translates the
Torque error into a diagnostics notification and pushes it to the
client.

Note that per specification, the server is responsible to manage the
state of all published diagnostics. This means that the server is
also responsible for clearing out previous notifications if they
become stale.

Bug: v8:8880
Change-Id: Ief46dc1d94d1e5b7fa3e0048df494bfc05974031
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1569434Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60942}