[5.1][Events] PageCache event classes

[Fedik]

Summary of Changes

Implementing Event classes for PageCache events. Affected events:

• [x] onPageCacheSetCaching
• [x] onPageCacheGetKey
• [x] onPageCacheIsExcluded

Testing Instructions

Enable PageCache plugin, make sure cache works as before

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:
• [ ] No documentation changes for docs.joomla.org needed
• [ ] Pull Request link for manual.joomla.org: TBD
• [ ] No documentation changes for manual.joomla.org needed

[HLeithner]

This pull request has been automatically rebased to 5.1-dev.

[crommie]

I have tested this item :white_check_mark: successfully on fa45c91c8358d23a151b769aa060d171fc74fa24

Caching keeps working as should.

---

_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/41965.}

[viocassel]

I have tested this item :white_check_mark: successfully on fa45c91c8358d23a151b769aa060d171fc74fa24

---

_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/41965.}

[richard67]

RTC

---

_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/41965.}

[bembelimen]

Thank you!