[TASK] Replace TYPO3 localization override with EXT:deepl_base

[sbuerk]

EXT:deepltranslate_core replaced TYPO3 backend implementation
of the localization JavaScript modal to add two custom modes to
the system along with extending the LocalizationController to
ensure processing works by mitigating the hardcoded core mode
checks implemented by the TYPO3 Core.

Meanwhile, a new planned extension also needs to provide one or
more custom modes, which should work standalone and or next to
EXT:deepltransate_core which makes providing hardcoded mode
extension unreliable, special in a cross-mix.

To mitigate this a new EXT:deepl_base extension has been now
created to provide the overrides in a extensible way using the
one or other PSR-14 event, adding a new AJAX Endpoint for the
locaization modes and adjusts the JavaScript to be dynamically
changeable and is based on a early work-in-progress change for
TYPO3 v14, provided as a early and slightly enhanced backport.

This change replaces the own implementation with the provided
events of the shared extension, dropping obsolete code directly
to keep it clean.

Current PSR-14 event based implementation lacks checking if
the deepl api key has been set and will be added with one
of the following changes along with further adjustments.

This change acts as a kickstart for the replacement now to
open up for dual developlment on this extension and another
extension on the same time and unblock that.

However, it's still a working state and leads to the direction
already planned.

Used command(s):

BIN_COMPOSER="Build/Scripts/runTests.sh -p 8.1 -t 12 -s composer -- " \
&& ${BIN_COMPOSER} config minimum-stability "dev" \
&& ${BIN_COMPOSER} config prefer-stable true \
&& ${BIN_COMPOSER} require "web-vision/deepl-base":"1.*.*@dev"
&& Build/Scripts/runTests.sh -p 8.1 -t 12 -s composerUpdate \
&& Build/Scripts/runTests.sh -p 8.1 -t 12 -s phpstanGenerateBaseline \
&& Build/Scripts/runTests.sh -p 8.2 -t 13 -s composerUpdate \
&& Build/Scripts/runTests.sh -p 8.2 -t 13 -s phpstanGenerateBaseline \
&& Build/Scripts/runTests.sh -p 8.1 -t 12 -s composerUpdate