extension_cli: Allow building without dynamically linking WebRTC (#13080)

This PR fixes an issue where the `zed-extension` CLI could no longer be
run as a static binary due to the following error:

```
dyld[36964]: Library not loaded: @rpath/WebRTC.framework/WebRTC
  Referenced from: <56332E1D-292E-3F9B-97B9-8A9962D21599> /Users/maxdeviant/projects/zed-extensions/zed-extension
  Reason: no LC_RPATH's found
fish: Job 1, './zed-extension --scratch-dir .…' terminated by signal SIGABRT (Abort)
```

This is the result of the addition of a dependency on `workspace` to the
`extension` crate (and thus, the `extension_cli` crate) in #12360.

Since we don't actually _need_ WebRTC in the extension CLI, we don't
care about dynamically linking it.

To resolve this, a new `no-webrtc` feature has been added to the
`live_kit_client` client crate and threaded through all of the crates
between it and the `extension_cli`.

Enabling the `no-webrtc` feature will prevent linking to the LiveKit
Swift SDK as well as linking the WebRTC framework.

Release Notes:

- N/A

crates/extension_cli/Cargo.toml

@@ -17,7 +17,7 @@ anyhow.workspace = true
 clap = { workspace = true, features = ["derive"] }
 env_logger.workspace = true
 fs.workspace = true
-extension.workspace = true
+extension = { workspace = true, features = ["no-webrtc"] }
 language.workspace = true
 log.workspace = true
 rpc.workspace = true