Simplify AI Event classes by using base classes
>>> [!note] Migrated issue
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Reported by: [murz](https://www.drupal.org/user/157092)
Related to !824
>>>
<h3 id="summary-problem-motivation">Problem/Motivation</h3>
<p>Now we have four event types:<br>
PostGenerateResponseEvent.php<br>
PostStreamingResponseEvent.php<br>
PreGenerateResponseEvent.php<br>
ProviderDisabledEvent.php</p>
<p>And most of them contain the same properties, getters, and setters, which leads to code duplication.</p>
<h3 id="summary-proposed-resolution">Proposed resolution</h3>
<p>Let's introduce base classes, containing the base properties, that are used in the events, instead of having the same code in each event.</p>
<h3 id="summary-remaining-tasks">Remaining tasks</h3>
issue