feat: update process_exec_tool_call() to take a cancellation token (#6972)

This updates `ExecParams` so that instead of taking `timeout_ms:
Option<u64>`, it now takes a more general cancellation mechanism,
`ExecExpiration`, which is an enum that includes a
`Cancellation(tokio_util::sync::CancellationToken)` variant.

If the cancellation token is fired, then `process_exec_tool_call()`
returns in the same way as if a timeout was exceeded.

This is necessary so that in #6973, we can manage the timeout logic
external to the `process_exec_tool_call()` because we want to "suspend"
the timeout when an elicitation from a human user is pending.








---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/openai/codex/pull/6972).
* #7005
* #6973
* __->__ #6972

codex-rs/core/src/codex.rs

@@ -3051,6 +3051,7 @@ mod tests {
         let session = Arc::new(session);
         let mut turn_context = Arc::new(turn_context_raw);
 
+        let timeout_ms = 1000;
         let params = ExecParams {
             command: if cfg!(windows) {
                 vec![
@@ -3066,7 +3067,7 @@ mod tests {
                 ]
             },
             cwd: turn_context.cwd.clone(),
-            timeout_ms: Some(1000),
+            expiration: timeout_ms.into(),
             env: HashMap::new(),
             with_escalated_permissions: Some(true),
             justification: Some("test".to_string()),
@@ -3075,7 +3076,12 @@ mod tests {
 
         let params2 = ExecParams {
             with_escalated_permissions: Some(false),
-            ..params.clone()
+            command: params.command.clone(),
+            cwd: params.cwd.clone(),
+            expiration: timeout_ms.into(),
+            env: HashMap::new(),
+            justification: params.justification.clone(),
+            arg0: None,
         };
 
         let turn_diff_tracker = Arc::new(tokio::sync::Mutex::new(TurnDiffTracker::new()));
@@ -3095,7 +3101,7 @@ mod tests {
                     arguments: serde_json::json!({
                         "command": params.command.clone(),
                         "workdir": Some(turn_context.cwd.to_string_lossy().to_string()),
-                        "timeout_ms": params.timeout_ms,
+                        "timeout_ms": params.expiration.timeout_ms(),
                         "with_escalated_permissions": params.with_escalated_permissions,
                         "justification": params.justification.clone(),
                     })
@@ -3132,7 +3138,7 @@ mod tests {
                     arguments: serde_json::json!({
                         "command": params2.command.clone(),
                         "workdir": Some(turn_context.cwd.to_string_lossy().to_string()),
-                        "timeout_ms": params2.timeout_ms,
+                        "timeout_ms": params2.expiration.timeout_ms(),
                         "with_escalated_permissions": params2.with_escalated_permissions,
                         "justification": params2.justification.clone(),
                     })