[!!!][FEATURE] Switch to standalone Fluid template engine

This change:

* Adds `typo3fluid/fluid` as dependency
* Converts system extension `fluid` to a so-called Fluid adapter
* Adds TYPO3-specific Fluid integrations as compatibility layer
* Turns Fluid's RenderingContext into a very flexible API
* Updates a few templates and core ViewHelpers for compatibility

On a more general level the change allows using a wide array of
new template syntaxes and integration features (see feature
documentation included with this commit in `core` extension).

The breaking changes are minimal; mostly caused by removal of
deprecated code from the `fluid` system extension (rather than
fundamental changes to how Fluid itself works). Custom templates
should work with little or no migration required.

Change-Id: Ib505cb66dabcc711868924d2fab3015ce549fbde
Releases: master
Resolves: #62940
Resolves: #69863
Resolves: #58752
Resolves: #48221
Resolves: #49903
Resolves: #54509
Resolves: #55343
Resolves: #55660
Resolves: #57446
Resolves: #70036
Resolves: #61144
Resolves: #60082
Resolves: #11287
Resolves: #70960
Resolves: #71552
Resolves: #67930
Resolves: #48656
Resolves: #71821
Resolves: #59540
Reviewed-on: https://review.typo3.org/42425


Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Reviewed-by: Marc Neuhaus <apocalip@gmail.com>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Reviewed-by: Xavier Perseguers <xavier@typo3.org>
Tested-by: Xavier Perseguers <xavier@typo3.org>
Reviewed-by: Alexander Opitz <opitz.alexander@googlemail.com>
Tested-by: Alexander Opitz <opitz.alexander@googlemail.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>