Use explicit-this in CRTP

[Tectu]

Since we moved from C++20 to C++23, we can now leverage "explicit-this" (or "deducing this") from P0847.

This can be used anywhere where we currently implement CRTP by manually passing the derived type into the base class.

From the top of my head:

• malloy::client::http::connection
• malloy::server::http::connection
• malloy::server::http::router_adaptor

Most likely everywhere where a grep for Derived will show a result.