[BC only] BPMN Editor - Refactor message bundles to match the *Constants.properties convention

Motivation
On the 11th of August all i18n translations (*Constants.properties) have to be "updated" in the code since the next few days we will send these to Memsource for translations.
Since we don't use Zanata anymore we have lost a little bit of CI for the translations. Now we do the whole process manually.
What is not in the *Constants.properties files until the 11.08.2021 (also day of 7.12.0.CR1 Feature Development Cutoff) will not have the chance of being translated into French, Spanish or Japanese for the 7.12.0.CR1
What you add later will be only available in English.
 
Action
Identify any message bundle that does not match the naming convention and address its refactor.

Acceptance criteria

• The identified message bundles that do not follow the naming convention must be renamed
• No changes in the UI are made