feat: Add guild_id parameter to Client.entitlements()

[lukenamop]

Summary

Entitlements can be owned by guilds that the bot is no longer a member of. The added guild_id parameter allows the Client.entitlements() function to filter by raw guild_id rather than requiring a Snowflake (guild) object.

Information

• 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, typehinting,
  examples, ...).

Checklist

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

[NeloBlivion]

This is not necessary as you can pass an Object to guild instead (as the only requirement is being a Snowflake, i.e. having an ID)

[lukenamop]

Fair enough. I didn't find that super intuitive but I guess it does work.

[lukenamop]

Got it working with discord.Object for now. I still think directly passing the ID would be more intuitive but this does work.