Fix: refactor plugin modals to dialogs to workaround J5.1 bug

[Ruud68]

Pull Request for Issue #9670 .

Summary of Changes

added new J5.1 dialogs when Joomla version is 5.1

Testing Instructions

test on both J5.1 and < J5.1

1. in back-end goto Kunena > plugins
2. click a plugin name

on J5.1 a dialog modal should open (save / save& close / close buttons on top
on < J5.1 a BS modal should open (buttons in the footer)

3. test if all buttons work.

The J5.1 plugin dialog modal is missing the Toggle inline help button (the BS modal has that button in the footer).
I have crated a PR for that in the Joomla repository: appreciate if you could also test that and if okay report back as positive test result on the Joomla repository: joomla/joomla-cms#43296

[xillibit]

It-is need to apply the PR4326 from Joomla! to test it ?

[Ruud68]

It-is need to apply the PR4326 from Joomla! to test it ?

No, not needed.
It should work without the Joomla PR.

The Joomla PR adds the button 'Toggle inline help' that is missing in the new 5.1 dialog modal.
You can test that separately if you have time and energy to do so :)