refactor: 全新预设系统、插件系统，实现多模态支持高度可自定义化的 AI 助手 (Sourcery refactored)

[sourcery-ai]

Pull Request #755 refactored by Sourcery.

If you're happy with these changes, merge this Pull Request using the Squash and merge strategy.

NOTE: As code is pushed to the original Pull Request, Sourcery will
re-run and update (force-push) this Pull Request with new refactorings as
necessary. If Sourcery finds no refactorings at any point, this Pull Request
will be closed automatically.

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To manually merge these changes, make sure you're on the refactor-v3 branch, then run:

git fetch origin sourcery/refactor-v3
git merge --ff-only FETCH_HEAD
git reset HEAD^

Help us improve this pull request!

[sourcery-ai]

Function ImageElement.__str__ refactored with the following changes:

• Lift code into else after jump in control flow (reintroduce-else)
• Replace if statement with if expression (assign-if-exp)

[sourcery-ai]

Function PoeAdapter.on_destoryed refactored with the following changes:

• Remove redundant conditional (remove-redundant-if)

This removes the following comments ( why? ):

# TODO: delete the bot