- load() should never be called directly but through service
- save and saveAs should return true result
- model manager gets to know model even before resolved

Fixes #81828

* experiments: add conditions for user settings and activation events

This adds two conditions we need for our js-debug experiment[1],
activation event frequency and a user setting check. The activation
events are stored in a rolling buffer containing a count over the past
week.

This PR contains unit tests but I wasn't totally sure how to verify it
by hand other than manually stubbing out experiments in OSS.

I also noticed the types for the instantionatService.stub were wrong if
we were passing a function to the service. I made a change to have
functions by spied upon and to return the spy, which is convenient and
closer to what the original `sinon.stub()` method does.

 1. https://github.com/microsoft/vscode-js-debug/issues/333

* fixup! keep experiment in evaluating state if not enough activations yet

* fixup! pr comments

Dropping a folder onto the editor should open a new tab (macOS) instead of a new window. (fix #90767)

Fixes #90883

fixes #87767