[4.0] Trigger the onBeforeExecute correctly through the dispatcher

[laoneo]

Pull Request for Issue #20435.

Summary of Changes

Sends the onBeforeExecute correctly in the applications.

Testing Instructions

Enable the language filter plugin.

Expected result

No exception is thrown.

Actual result

Exception
Argument 1 passed to PlgSystemLanguageFilter::onBeforeExecute() must be an instance of Joomla\CMS\Event\BeforeExecuteEvent, instance of Joomla\Event\Event given
is thrown.

[infograf768]

I have tested this item ✅ successfully on 3fbe042

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[infograf768]

@mbabker @wilsonge This one is rather urgent if we want to test associations and solve the multilingual issues

[roland-d]

I have tested this item ✅ successfully on ac6b179

Before the fix after I activated the plugin it was impossible to access Joomla, after the fix everything worked as expected.

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[ghost]

@infograf768 can you please retest?

[wilsonge]

This one doesn't work sadly :( The getContainer doesn't exist in this class

[rdeutz]

I made a PR to fix it