Testrunner: Accept test_name by run-test number

The change allows the testrunner to accept test numbers for running
a particular test. It runs all the tests for which the prefix matches
with the passed test name.

For test name "001-H", it will run 001-HelloWorld
However, for test name "001", it will run 001-Main and 001-HelloWorld

If it doesn't find any test with matching prefix, it raises ValueError.

Test: Verified by running locally
Bug: 35260706
Change-Id: Ib132d6635b22ade1fd96728ba629fe7d580ba6cf