Restrict Harm category to the sublist only Gemini support

[aertoria]

Description of the change

Fork safety_tpes and palm_safety_types

The combined HarmCategory enum makes everything worse. Can we split them?

Motivation

Create a subcategory of the list of harm category so that user will not confuse with the Palm ones.

Type of change

Choose one: Feature request

Checklist

• I have performed a self-review of my code.
• I have added detailed comments to my code where applicable.
• I have verified that my change does not break existing code.
• My PR is based on the latest changes of the main branch (if unsure, please run git pull --rebase upstream main).
• I am familiar with the Google Style Guide for the language I have coded in.
• I have read through the Contributing Guide and signed the Contributor License Agreement.