add __repr__ method to various classes

[owocado]

Summary

This adds __repr__ dunder method to following classes to help with bot development and debugging:

• AppCommandContext
• AppInstallationType
• AppCommandPermissions
• GuildAppCommandPermissions
• InteractionCallbackResponse
• Parameter from ext.commands module

Please let me know if this is ok as-is or should I split these 5 additions into individual PRs to preserve atomicity/git blame.

Moreover, the reason I used self.__class__.__name__ in repr of Parameter is because if people are already subclassing that class in their projects for customization, not sure. Let me know if I should change it.

Bikeshedding post: https://discord.com/channels/336642139381301249/1355473537577652234

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• 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, ...)