ANDROID: Update the kselftest.sh with options to specifiy serial & test.

Add device serial number parsing from acloud command output.

Add -t flag to run only specified test.

Update the TESTSDIR.

Signed-off-by: Betty Zhou <bettyzhou@google.com>

Test: local test
Bug: 309421656
Change-Id: I6523f1a2135fee7d10dee0d1a8e08236ea49f535