zlog: Init (#27273)

Scaffolding for a revised way of logging in Zed. Very WIP, but the idea
is to allow maintainers to tell users to paste
```json
{
    "log": {
        "project.format": "trace"
    }
}
```
into their settings so that even trace logs are emitted for the log
statements emitted from a logger under the `project.format` scope.

The plan is to eventually implement the `Log` trait from the `log` crate
instead of just wrapping the `log` crate, which will simplify the
implementation greatly, and remove our need for both the `env_logger`
and `simplelog` crates.
Additionally, work will be done to transition to using the scoped
logging APIs throughout the app, focusing on bug hotspots to start
(currently, scoped logging is only used in the format codepath).

Release Notes:

- N/A

crates/zed/Cargo.toml

@@ -135,6 +135,7 @@ welcome.workspace = true
 workspace.workspace = true
 zed_actions.workspace = true
 zeta.workspace = true
+zlog_settings.workspace = true
 
 [target.'cfg(target_os = "windows")'.dependencies]
 windows.workspace = true