fix(ext/node): handle multiple calls in inspector.Session.post() (#31067)

Fixes a panic that occurred when using nested session.post() calls in
the node:inspector module. The issue manifested when callbacks from
inspector commands (like Profiler.enable) called session.post() again,
causing a re-entrant invocation of op_inspector_dispatch.

Fixes https://github.com/denoland/deno/issues/31020