refactor(appinfo)!: improve application models

[shiftinv]

Summary

Refactors application models, deduplicating and generally merging related code.

The diff is fairly unreadable as-is, skipping the first commit (that just moves PartialAppInfo above AppInfo) improves readability quite a bit.

tl;dr on the important changes, see changelog for everything:

• new hierarchy: PartialAppInfo < AppInfo < BotAppInfo (where BotAppInfo is equivalent to the old AppInfo)
  • note: this shouldn't have any practical effect on user code unless these types are created there
• AppInfo.summary is no more (deprecated in previous version)
• Invite.target_application (which is now AppInfo) contains more fields
• now using the correct cover_image url format

Checklist

• If code changes were made, then they have been tested
  • I have updated the documentation to reflect the changes
  • I have formatted the code properly by running task lint
  • I have type-checked the code by running task pyright
• This PR fixes an issue
• This PR adds something new (e.g. new method or parameters)
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, ...)

[onerandomusername]

Might it be worth caching this information? IIRC we receive the full app info on on_ready/identify when we receive the flags of the application. If not, it may be worth caching this information anyways (due to the ext.commands extension using it anyways, and this information being quite useful regardless)

[shiftinv]

Caching this should be up to users, since the data could change at any time - ext.commands already caches the owner/owners, which is the only part it currently needs, and the ready event only contains app ID + flags :/

[onerandomusername]

@shiftinv would you please resolve conflicts?

[shiftinv]

would you please resolve conflicts?

@onerandomusername done.

[onerandomusername]

@shiftinv would you please resolve conflicts again?

[onerandomusername]

@shiftinv Would you please resolve conflicts?

[onerandomusername]

I promise I'll review it this time.