AI content suggestion->Alter tone: Ability to choose multiple vocabularies

Problem/Motivation

We can select only one vocabulary for the "Alter tone". There could be use cases when we need the taxonomy terms from multiple vocabularies, but the flexibility of choosing multiple vocabularies is not present yet.

Steps to reproduce (required for bugs, but not feature requests)

• Enabled AI Content suggestions module
• Go to settings /admin/config/ai/suggestions
• Enable the Alter tone "Enable Alter tone"
• Check the checkbox "Choose own vocabulary for tone of voice options."
• Select list appears where you can choose only one vocabulary from the list

Proposed resolution

Ability to choose more than one vocabulary.

Remaining tasks

TBD

Optional: Other details as applicable (e.g., User interface changes, API changes, Data model changes