replace Junit 4 by Junit 5 : remove useless dependencies in build.gradle and fix import & assertion in ConfigParserTest.java

Fix some warning/issue about logback in junit test by renaming logback.xml into logback-test.xml and removeing useless appender inside it

rewrite constructor of Process.java, PreparationProcess.java and update DeviceHelper to use new constructor

add loadPreparationProcess  in DeviceHelper.java & and replace PreparationProcess.putSourceToDownload(String, RomSource) by setSourceToDownload(HashMap<String, RomSource)

Update docker file to use channel 5.x

See merge request e/tools/easy-installer!139

Currently translated at 100.0% (252 of 252 strings)

Translation: /e//Easy Installer
Translate-URL: https://i18n.e.foundation/projects/e/easy-installer/de/

remove unused method, unused import from many classes. Also replace ThreadFactory.getProcessMould() by Phone.getProcess()

remove MainWindowController 'flashed' property and related getters/setters as duplicate of device.flashed