Easily parsable test list

Whe using `--gtest_list_tests`, the list is split into the test suite on one line, and individual test names on separate lines. This makes it harder to parse the output for listing all available tests. Maybe there should be an option to list the tests using their full names, so that instead of this:
```
TestSuite1.
Test1
Test2
TestSuite2.
Test1
```
we can get this:
```
TestSuite1.Test1
TestSuite1.Test2
TestSuite2.Test1
```

Start by tracing the --gtest_list_tests entry point and its current suite-and-test output. Determine how an option for fully qualified names should be exposed, then verify that the output lists each test as TestSuite.Test on its own line while preserving the existing behavior.

Written by the indexing model from the issue text.