Collapse runnable test lenses if a macro creates too many

[Veykril]

Currently when a macro invocation creates more than one runnable test lens we give the lenses the functions name and still show them like here:

This works fine for a small number of lenses but can quickly become overwhelming, includeing bindgen output is a prime example for this:

Instead we should collapse these into one special lense that offers a selection on which test to run if a macro expands to X or more lenses.

[godcodehunter]

microsoft/vscode#3220
microsoft/vscode#66418
It may be useful for better user interaction