This change adds an ExecutionHandler hook to the Go chain orchestrator,
allowing direct callers to wrap each interceptor/invoke RPC call. The
handler can inspect and modify invoke params before execution, inspect
results after execution, override the effective mode per-invocation, or
short-circuit execution entirely. The change is fully
backwards-compatible and requires no SEP/protocol modifications.
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Signed-off-by: Ukjae Jeong <jeongukjae@gmail.com>
77a8464b33