refactor: revamp picker block

[lawvs]

Description

I'm really sorry for submitting such a big change without any substantial feature updates in the pull request.

Initially, I planned to fix the issue with the picker component not being able to select items using the arrow keys. However, during development, I discovered that VarReferenceVars may have multiple nested structures, making it challenging to handle properly with LexicalTypeaheadMenuPlugin.

This PR still includes many useful updates. If you have time, I hope this PR can be merged.

This PR mainly affects the following areas:

• Fixed the issue with PickerBlock not scrolling along (by adjusting the usage of floating-ui).

Screen.Recording.2024-05-11.at.17.11.40.mov

• Removed redundant code by merging PromptMenu and VariableMenu into PickerBlockMenuOption.

These changes improve the code structure and organization of the picker block functionality.

Type of Change

• Improvement, including but not limited to code refactoring, performance optimization, and UI/UX improvement

How Has This Been Tested?

Input '/' and test the picker block plugin in the prompt editor.

Suggested Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods
• optional I have made corresponding changes to the documentation
• optional I have added tests that prove my fix is effective or that my feature works
• optional New and existing unit tests pass locally with my changes