Add client::zed_urls module for constructing zed.dev URLs (#19391)

This PR adds a new `zed_urls` module to the `client` crate.

This module contains functions for constructing URLs to Zed properties,
such as zed.dev.

The URLs produced by this module will respect the server URL set via
settings or the `ZED_SERVER_URL` environment variable. This allows them
to correctly reflect the current environment (such as when testing Zed
against a local collab/zed.dev).

Release Notes:

- N/A

crates/client/src/client.rs

@@ -4,6 +4,7 @@ pub mod test;
 mod socks;
 pub mod telemetry;
 pub mod user;
+pub mod zed_urls;
 
 use anyhow::{anyhow, bail, Context as _, Result};
 use async_recursion::async_recursion;