Currently, when generating and propagating view updates, if we notice
that we've already exceeded the time limit, we throw an exception
inheriting from `request_timeout_exception`, to later catch and
log it when finishing request handling. However, when catching, we
only check timeouts by matching the `timed_out_error` exception,
so the exception thrown in the view update code is not registered
as a timeout exception, but an unknown one. This can cause tests
which were based on the log output to start failing, as in the past
we were noticing the timeout at the end of the request handling
and using the `timed_out_error` to keep processing it and now, even
though we do notice the timeout even earlier, due to it's type we
log an error to the log, instead of treating it as a regular timeout.
In this patch we make the error thrown on timeout during view updates
inherit from `timed_out_error` instead of the `request_timeout_exception`
(it is also moved from the "exceptions" directory, where we define
exceptions returned to the user).
Aside from helping with the issue described above, we also improve our
metrics, as the `request_timeout_exception` is also not checked for
in the `is_timeout_exception` method, and because we're using it to
check whether we should update write timeout metrics, they will only
start getting updated after this patch.
Fixes#19261
(cherry picked from commit 4aa7ada771)
Closesscylladb/scylladb#19262
813fef44d3