Feature: #69568 - FormEngine data processing

Description

Warning: The FormEngine data structure will change in the future and extensions must not rely on array or class structures at the moment.

The FormEngine construct to render records has been split to two main parts where the first data processing part takes care of gathering and processing all data needed for the second part to render final form data.

The data processing is done via FormDataCompiler that returns a data array that can be given to the outer most render container. The array contains all main data required by the render part like final TCA as well as the processed database row.

Extensions can change the data processing by registering additional items in the data processing chain. For casual TCA based database records, the FormDataGroup TcaDatabaseRecord is used to define relevant data provider within $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord']. Additional data provider can be added at specific positions using the depends and before keywords relative to other providers.