[backport 11.0] several code paths handle resources using system Charset rather than UTF-8

To reproduce:

• Create a new project from the 4.1.0-SNAPSHOT archetype
• Add "<file.encoding>US-ASCII</file.encoding>” to the “systemProperties” section in the main pom
• Build & start the project
• Using Essentials, add the “Banners” feature, no need to rebuild & restart
• Two issues:
  • In the console, at http://localhost:8080/cms/console/?1&path=/hippo:configuration/hippo:translations/hippo:templates/fr you see that the label for "new-banner-document” is incorrectly imported as "nouvelle banni??re”, and you see this in the CMS as well
  • On the site, the footer contains an incorrectly copied © character, displayed as ?? (see screenshot in ESSENTIALS-994)