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/debug_adapter_extension/src/extension_dap_adapter.rs

@@ -6,6 +6,7 @@ use std::{
 
 use anyhow::{Context, Result};
 use async_trait::async_trait;
+use collections::HashMap;
 use dap::{
     StartDebuggingRequestArgumentsRequest,
     adapters::{
@@ -91,6 +92,8 @@ impl DebugAdapter for ExtensionDapAdapter {
         user_installed_path: Option<PathBuf>,
         // TODO support user args in the extension API
         _user_args: Option<Vec<String>>,
+        // TODO support user env in the extension API
+        _user_env: Option<HashMap<String, String>>,
         _cx: &mut AsyncApp,
     ) -> Result<DebugAdapterBinary> {
         self.extension