Attach to pid picker - bodyblock users who are not in the new debugger experiment

[kimadeline]

Work item created from the attach-to-pid spike #8909

@karthiknadig @luabud We need to decide what we want to show to users who manually add an attach-to-pid debug config, but are not in the DA experiment.

[luabud]

The idea is that starting on next release every user will be in the DA experiment. We would only have that problem for insiders users then, right?

[luabud]

Nope, it should be in the PtvsdWheels37 experiment. So let's display the following prompt:

"Attaching the debugger to a local process is an experimental feature. It will be available to all users soon."

[karthiknadig]

Validated.