[Java] Add missing Locale to String.format() invocations

[joschi]

When called without a specific locale, String.format() will use the system default locale which doesn't make sense with English messages in our Mustache templates.

This will also cause warnings/failures when using static analysis tools such as Forbidden API Checker:

Forbidden method invocation: java.lang.String#format(java.lang.String,java.lang.Object[]) [Uses default locale]
  in com.example.model.MyModelDeserializer (MyModelDeserializer.java:145)

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[Chrimle]

Correct me if I am wrong, but the Locale is only needed for the {{#supportUrlQuery}}-block, but every single model now have import java.util.Locale;.

Could there potentially be a {{#supportUrlQuery}}-block around the import-statement as well?

Created #22313

[joschi]

@Chrimle Maybe you could provide a PR for that. 😄