[tracking] Media Type improvements

[yoshuawuyts]

This is a tracking issue for a variety of improvements to how we handle media types in http-types:

• Rename Mime to MediaType (semver major) rename Mime to MediaType #251
• Add Mime::into_extension Add Mime::into_extension #271
• Port mime-db to Rust to enhance our mime extension guessing Port mime-db to Rust to enhance our mime extension guessing #272
• Add Mime::is_compressible method Add Mime::is_compressible method #273