docs(cast): add description for cast rpc --decode-internal (#11825)

Author: wellnana

crates/cast/src/cmd/call.rs

@@ -97,6 +97,12 @@ pub struct CallArgs {
     #[arg(long, requires = "trace")]
     debug: bool,
 
+    /// Identify internal functions in traces.
+    ///
+    /// This will trace internal functions and decode stack parameters.
+    ///
+    /// Parameters stored in memory (such as bytes or arrays) are currently decoded only when a
+    /// single function is matched, similarly to `--debug`, for performance reasons.
     #[arg(long, requires = "trace")]
     decode_internal: bool,