Make context element mandatory when showing a context menu.

[tsmaeder]

What it does

This PR makes the context menu argument when showing a context menu mandatory. This is necessary to attach the context menu to the correct window when extracting widgets to secondary window. If now context element is available at a call site, clients can just pass window.document.body as the context.

Fixes #14960

How to test

Check that context menus everywhere are shown in the correct location and have the correct content for the location of the menu. This also includes "more" menus on toolbars, etc. (i.e. all menus other than the main menu bar. Where available, check that the menus work in secondary windows.

Follow-ups

Breaking changes

• This PR introduces breaking changes and requires careful review. If yes, the breaking changes section in the changelog has been updated.

Attribution

Contributed on behalf of STMicroelectronics

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]

works for me! thanks!