feat(bot.py): fix type issues

[EmreTech]

Summary

This PR fixes the (many) type issues in bot.py and a few type issues in commands/core.py. This PR also makes the code more efficient and readable with issues that aren't entirely type related.

Information

• [x] This PR fixes an issue.
• [ ] This PR adds something new (e.g. new method or parameters).
• [x] This PR is a breaking change (e.g. methods or parameters removed/renamed).
• [ ] This PR is not a code change (e.g. documentation, README, typehinting, examples, ...).

Checklist

• [x] I have searched the open pull requests for duplicates.
• [ ] If code changes were made then they have been tested.
  • [x] I have updated the documentation to reflect the changes.
• [x] If type: ignore comments were used, a comment is also left explaining why.