feat: add safety alerts channel to guild model

[ItsRqtl]

Pull Request Type

• Feature addition
• Bugfix
• Documentation update
• Code refactor
• Tests improvement
• CI/CD pipeline enhancement
• Other: [Replace with a description]

Description

This PR adds safety alerts channel related stuff to the Guild model.

Changes

• added safety_alerts_channel_id field
• added safety_alerts_channel property
• added safety_alerts_channel args to Guild.edit method
• added safety_alerts_channel_id args to http.modify_guild method

Related Issues

Test Scenarios

Get a guild that has a safety alerts channel set, check the safety_alerts_channel is equal to the one being set
Edit the guild with the Guild.edit method, check if Guild.safety_alerts_channel == the one being passed into Guild.edit

Python Compatibility

• I've ensured my code works on Python 3.10.x
• I've ensured my code works on Python 3.11.x

Checklist

• I've run the pre-commit code linter over all edited files
• I've tested my changes on supported Python versions
• I've added tests for my code, if applicable
• I've updated / added documentation, where applicable