Summary
A new version of `vscode-extension-tester` was released, so let's use it in our tests. Also update `@vscode/test-electron` (AKA `vscode-test`).

Note
There is a note that it might be needed to increase timeouts because of some changes mentioned in known issues, but it looks fine both locally and on CI/CD.

AC
The version is bumped and tests are running correctly.