[Telemetry] Add error handling to DiagnosticRoutine

This change adds the os.diagnostics.onRoutineException callback
and its invocation from DiagnosticRoutine.

Bug: b/286031590, b/294819343
Test: browser_tests
--gtest_filter="*TelemetryExtensionDiagnosticRoutineObserverBrowserTest*"

NO_IFTTT=Documentation for this change will be done in one batch
Low-Coverage-Reason: Tests for the error callback will be added in
subsequent patches.

Change-Id: Idf2bf4fb0a2962f37c8662204bf93941cc27f75c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4783812
Reviewed-by: Ethan Cheng <yycheng@google.com>
Commit-Queue: Bastian Kersting <bkersting@google.com>
Reviewed-by: Giovanni Ortuno Urquidi <ortuno@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1188998}