fix(bridge): instanceof Promise was not giving correct results when run with Jest

[mjameswh]

What was changed

• Bridge's error conversion logic now uses the isPromise node's utility function instead of an instanceof Promise check.

  The later is prone to Jest's globals differ from Node globals bug (i.e. somePromise instanceof Promise may evaluate to false in some contexts), which would result in not converting errors thrown from the Rust side when Worker is run in Jest.

  This has been causing Jest tests to fail with ShutdownError: Worker has been shutdown errors, using TS SDK 1.12.0.