fix: allow delete_after for ephemeral messages

[AstreaTSS]

Pull Request Type

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

Description

This PR allows using delete_after for ephemeral messages, which previously produced an error due to not passing the context in for message.delete(...). This uses a purposely hidden kwarg to do so - let me know if that needs to be changed.

Changes

• Use a hidden kwarg for SendMixin to determine if the mixin should pass in itself for message.delete(...). I figured it was better than using an isinstance and potentially maybe causing recursive imports.
• Make InteractionContext and HybridContext pass this value as appropriate.

Related Issues

Fixes #1465.

Test Scenarios

• Send an ephemeral message through a slash command (broken on hybrid commands due to a different bug that will be PRed shortly).
• Use delete_after while sending.

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