Consider removing type and label from IRawEnvAdapter

[isidorn]

Also check whether some debug extension is actually using the type and label as platform specific in their package.json.

If not we might want to consider to move "type" and "label" to "IRawAdapter" (where other non-platform specific attributes live).

[weinand]

The IRawAdapter got renamed to IDebuggerContribution and the code that deals with platform specific package.json attributes neither handles 'type' or 'label'.

[isidorn]

@weinand I have remove the type and label from the IPlatformSpecific interface. Note that I have added some return types to methods because I like to always explicitly write them even for void. And I prefer destructured imports so I also changed that a bit.