[vscode] Add WindowState active in plugin API

[rschnekenbu]

What it does

Implements the new VS Code API WindowState Active

Fixes #13692

Contributed on behalf of ST Microelectronics

How to test

This can be tested with the following extension:

• src: window-activestate-sample-0.0.1-src.zip
• zip vsix: window-activestate-sample-0.0.1.zip

This extension will display a notification has soon as window state is changed, focus or active. To test, you can get or lose focus with any combination of idle time to check activity state. User is considered as inactive after 20sec of doing nothing, and this timer will be reset has soon as a mouse button is clicked / key stroke or touch gesture.

Follow-ups

None

Review checklist

• [x] As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• [ ] As a reviewer, I agree to behave in accordance with the review guidelines

[rschnekenbu]

Thanks for your review, @msujew ! Good catch for the logic of the reset. I changed the inactivity check interval to 1sec and extended the number of checks to 30.