fixes ISSUE-47093: Remove guava usage from backoffice java code

• InitialSetupUtility
  • Stop using Charsets.UTF_8 constants from guava library. Instead use standard java StandardCharsets class
  • Simplify reading file by using Files.ReadString(Path,Charset) directly avoid the intermediate byte[]
• CrossOrganizationReference
  • Use standard Collections.reverse method instead of guava Lists.reverse Note that JDK function modify the argument in place instead of returning a 'reversed' view. However with that usage here (cleanup after unit-tests & .clear()-ing the list just afterwards no need to clone the list.
• AllowedOrganizationTest
  • Change away from guava ImmutableMap.builder() replace it by standard java
    • Map.Of(Key,Value,Key,Value, ...) for the simple case
    • Map.ofEntries for the slightly more complex case.

Try run: https://builds.openbravo.com/view/try/job/try-init/873/