CTest integration: Add option to list all tests

[LDong-Arm]

Is your feature request related to a problem? Please describe.

We will soon be using CTest to automatically build all tests in Mbed OS with CMake and run them with greentea/htrun. While it will be possible to manually trigger them with a full ctest command line, an option in mbed-tools makes it user friendly.

This task is specific to listing all tests.

Describe the solution you'd like

Interfacing with the ctest command.

Describe alternatives you've considered

An alternative is running ctest directly, but as described above, a option in mbed-tools has been requested.

Additional context