Feature: #87748 - Add SiteProcessor

See Issue #87748

Description

A new Site Processor has been introduced which can be used to fetch data from the site entity

tt_content.mycontent.20 = FLUIDTEMPLATE
tt_content.mycontent.20 {
   file = EXT:myextension/Resources/Private/Templates/ContentObjects/MyContent.html

   dataProcessing.10 = TYPO3\CMS\Frontend\DataProcessing\SiteProcessor
   dataProcessing.10 {
      as = site
   }
}

In the Fluid template the properties of the site entity can be accessed

<p>{site.rootPageId}</p>
<p>{site.someCustomConfiguration}</p>