lsp-config: Allow setting a server's environment variables (#27213)

Closes https://github.com/zed-industries/zed/issues/14334, allowing
users to set environment variables for a language server binary like:

```json
"lsp": {
  "rust-analyzer": {
    "binary": {
      "path": "/Users/dbarsky/.cargo/bin/rust-analyzer",
      "env": {
        "RA_PROFILE": "*>100"
      }
    },
  }
}
```

The newly introduced environment variables are merged with the shell
environment. Perhaps more controversially, I've _also_ removed the
trimming/`stderr:`-prefixing of language server logs. This because
rust-analyzer has some nice, tree-shaped profiling built-in, and it
prevents us from printing profiles like this:

<details>
<img width="1147" alt="Screenshot 2025-03-20 at 12 09 14 PM"
src="https://github.com/user-attachments/assets/b7066651-6394-492b-b745-906c66d3c7b2"
/>
</details>

Release Notes:

- Added the ability to set a language server's environment variables.
- Removed the `stderr`-prefix of a language server's stderr logs.

crates/extension_host/src/wasm_host/wit/since_v0_3_0.rs

@@ -651,7 +651,7 @@ impl ExtensionImports for WasmState {
                             binary: settings.binary.map(|binary| settings::CommandSettings {
                                 path: binary.path,
                                 arguments: binary.arguments,
-                                env: None,
+                                env: binary.env,
                             }),
                             settings: settings.settings,
                             initialization_options: settings.initialization_options,