[Android] Report NOTRUN for missing tests after instrumentation run

This changes the reported statuses from UNKNOWN to NOTRUN to match the
definition in //build/util/lib/results/result_types.py, for missing
tests in a finished instrumentation run.

The correct set of UNKNOWN tests (which we know they have started) in
a run are already detected in GenerateTestResults in
//build/android/pylib/instrumentation/instrumentation_test_instance.py

Batched (or individual) reruns are present in the test logic no matter
what status is reported here.

Bug: 1410586
Change-Id: Iddf22cc8e87ae2fdd0804892eb13ea9ac5ce7627
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5042079
Reviewed-by: Haiyang Pan <hypan@google.com>
Commit-Queue: Zhaoyang Li <zhaoyangli@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1243066}