Migration to Vue 3 (again)

This is more organized and cleaned up version of previous attempt (which was, pretty much a deep dive head-first into toilet bowl).

This should mostly work, but certain things are really broken rn; I'll keep a list:

• Sticker picker completely broken
  • This is caused by (again) tab-switcher. I will need to change it AGAIN to pre-render its slot and iterate over that since it pretty much iterates on some sort of not-fully-realized template (?)
• Tabs can't be disabled (?) see above, visible on user profile page - "media" tab always enabled.
• Transitions/animations do not work
• Anything that uses with_load_more doesn't work. Something to do with slots
  • Followers/following tabs in user profiles
  • Pretty much the entirety of Mutes/Blocks tab in settings
  • Listeners aren't passed (not sure if needed at all)
• Chat message view is broken (???)
• Some routing is somewhat broken (notably - the fancy urls end up being /(users/)?username)
  • Fixed the (users/)? part but there's more like it i believe.
• Tooltip for scope icon (in statuses) no longer capitalized. Needs proper i18n
• Interactions view doesn't have tab switcher (grrr)
• Some i18n warnings in some places (not with compat build)
• Some warnings about events emitted not being declared (not with compat build)
• Serviceworker untouched, definitely doesn't work (compiles now but not sure if works)
• Minor spacing errors, most likely due to spaces always being dropped
• Theme tab is broken (not with compat build)
• Post content type selects show empty by default
• Inline usercards don't open instead direct to user profile page immediately
• Show Advanced checkmark doesn't work
• Fixed tests... mostly. Shit's as stable as box of dynamite though. Seems like mocha is less supported now and compat build might be interfering with vue/test-utils

This list is incomplete, you can help by expanding it