Implement the classic stage editor

[andy840119]

Guess should implement the editor while thinking #1764
And can start implement this shit after add the new layout class in the #1755.

prepare:

• Classic layout modal implementation. -> Handle in the Implement stage class as metadata in the karaoke beatmap #1755.
• Design the figma page for it.
  • Not really sure will use the same screen for different layout? -> maybe just named classic layout editor screen.

[andy840119]

Maybe what is this shit looks like.

[andy840119]

诶不是
怎麼感覺沒有結束的一天

[andy840119]

todo:

• Implement classic stage generator.
• Implement classic stage change handler. -> Implemented in the Implement classic stage changer handler #1825.
• Implement the checks for the stage category. -> Implemented in the Implement classic layout checks. #1826.

[andy840119]

Note:
Should implement the timing part for the #1828.

[andy840119]

todo:

• Need to think about should combine the layout and timing into single editor?