chore: [tests] update some BrowserWindow tests
chore: [tests] update some BrowserWindow tests

- manually close an existing windows before creating a new one.
  We have to do it because the `afterEach` hook doesn't get called
  if a test fails.
- add some async/await goodies

the-ress/electron,bpasero/electron,the-ress/electron,electron/electron,gerhardberger/electron,electron/electron,gerhardberger/electron,bpasero/electron,electron/electron,gerhardberger/electron,seanchas116/electron,shiftkey/electron,gerhardberger/electron,electron/electron,shiftkey/electron,shiftkey/electron,the-ress/electron,electron/electron,gerhardberger/electron,seanchas116/electron,shiftkey/electron,the-ress/electron,shiftkey/electron,shiftkey/electron,the-ress/electron,seanchas116/electron,electron/electron,gerhardberger/electron,bpasero/electron,electron/electron,bpasero/electron,gerhardberger/electron,bpasero/electron,seanchas116/electron,bpasero/electron,bpasero/electron,the-ress/electron,the-ress/electron,seanchas116/electron,seanchas116/electron