[5.0][Events] Extension ChangeState event

[Fedik]

Summary of Changes

Add missing event for onExtensionChangeState
Was missing in:

• [5.0][Events] Extension and Installer event classes #41322

Testing Instructions

Go to extension manager,
Try publish/unpublish extension.

Actual result BEFORE applying this Pull Request

Works

Expected result AFTER applying this Pull Request

Works

Link to documentations

Please select:

• Documentation link for docs.joomla.org: https://docs.joomla.org/Plugin/Events#Extensions
• No documentation changes for docs.joomla.org needed
• Pull Request link for manual.joomla.org: New Event classes Manual#177
• No documentation changes for manual.joomla.org needed

[HLeithner]

thx