Update various things to fix tests

- Update `vscode-test` to `@vscode/test-electron`
  (fixes downloading VS Code problem on Windows)
- Update `vscode-extension-tester` to latest version
  (fixes "cannot install extension" on Linux)
- Update `@types/node` to ^18
  (needed to get everything compiling after updating to vscode-extension-tester)

Signed-off-by: David Thompson <davthomp@redhat.com>

Author: datho7561