Make web::Path innards public

[IriaSomobu]

PR Type

Other?

PR Checklist

• [x] Tests for the changes have been added / updated.
• [x] ~Documentation comments have been added / updated~
• [x] A changelog entry has been made for the appropriate packages.
• [x] Format code with the latest stable rustfmt.
• [x] (Team) Label with affected crates and semver status.

Overview

This change allows us to do something like this:

async fn delete_channel_message(
    web::Path((channel_id, message_id)): web::Path<(Snowflake, Snowflake)>,
) {
  // here channel_id and message_id are Snowflakes,
  // and not web::Path<Snowflake>
}

Dunno why other web types are public and this is not.