dap: Allow user to pass custom envs to adapter via project settings (#40490)

It is now possible to configure logging level of CodeLLDB adapter via
envs specified in project settings like so:

```
{
    "dap": {
        "CodeLLDB": {
            "envs": {
                "RUST_LOG": "debug"
            }
        }
    }
}
```

Release Notes:

- N/A

crates/settings/src/settings_content/project.rs

@@ -154,6 +154,8 @@ pub struct DapSettingsContent {
     pub binary: Option<String>,
     #[serde(default)]
     pub args: Option<Vec<String>>,
+    #[serde(default)]
+    pub env: Option<HashMap<String, String>>,
 }
 
 #[skip_serializing_none]