[TASK] Replace TYPO3 localization override with EXT:deepl_base

`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):

```shell
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
```

Author: sbuerk