[vscode] dropdown menu for executable/test selection

[daminetreg]

The vscode plugin should provide an executable selection to run the tests ( as currently the cmdline presents the built binaries ) it could provide them in the vscode plugin as well.

On the command line it's possible to say : tipi build . -t linux --monitor -o some_test --test some_test, enabling this selection to be done directly from the graphical editor would be a better experience.

This has been discussed in a separate thread with @GregorPfirter-EH.