Support to call debug adapter API from extension

[weinand]

[isidorn]

Assigning to november to investigate

[roblourens]

What's your current thinking about how the extension/debug adapter communication should work for skipFiles?

[weinand]

@roblourens since the skip-files-ui-feature is a one-off private feature, you are free to introduce whatever protocol you need. Only your debug adapter will use it.