Do not dispose dialogs on close

[tsmaeder]

What it does

Fixes #12093

The about dialog in Theia is reopened and must no be disposed on close. This PR overrides the onCloseRequest method from BaseWidget to not invoke dispose(). In order to minimize impact for clients of the API, I've added an optional parameter to the open() method that controls whether the dialog is disposed when it is closed.
This change might be breaking in the case where clients reuse dialog instances and do not rely on open() to show the dialog. In that case, they will have to dispose the dialog themselves now. That should be a very rare case, though.

Contributed on behalf of STMicroelectronics

How to test

• Open and close the about dialog at least three times. Make sure there are not messages and exceptions in the browser log.
• Test behavior of both dismissing and accepting dialogs, for example
  • ConfirmationDialog: I used the "Clear editor history" commnand
  • Add a function breapoint in the "breakpoints" view
  • Make an editor dirty and close it: there is a dialog asking whether to save
    Ensure these scenarios work correctly in the browser and Electron case.

Follow-ups

• Refactor BaseWidget lifecycle #14455

Review checklist

• 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

[sdirix]

Thanks for the changes.

I tested all mentioned scenarios in the browser. There I could not see any errors.

I also tested all mentioned scenarios in Electron. There I was able to reproduce the following error when opening the about dialog multiple times: ERROR Warning: You are calling ReactDOMClient.createRoot() on a container that has already been passed to createRoot() before. Instead, call root.render() on the existing root instead if you want to update it. The other test scenarios did not produce any errors.