fix(28833): Ensure JSONSchema examples are array

[vanch3d]

See https://hivemq.kanbanize.com/ctrl_board/57/cards/28833/details/

There is a conflict in the definition of the examples keyword between the two versions of JSONSchema

• v6 : examples?: JSONSchema6Type[] | undefined;
• v7 : examples?: JSONSchema7Type | undefined;

The documentation for the validator used in the RJSF (AJV) states for v7 (https://ajv.js.org/json-schema.html#draft-07):

examples: an array of data instances. Ajv does not check the validity of these instances against the schema.

and validates the property as an array. This results in several schemas being rejected by the topic filter UX

The PR ensures that every examples property handled by the frontend is created as an array of values

Out-of-scope

• Externally created schemas might still be generated with a different version of JSONSchema. A "converter" will certainly be needed to handle such differences properly. It will be done in a future ticket