fix(v7): Allow removal of message listeners on utility processes

[timfish]

Backport of #1472 to v7. Fixes #1466 for the 7.x line.

configureUtilityProcessIPC() replaced child.on with a Proxy that registered an anonymous wrapper around each message listener to hide the SDK's handshake message. off and removeListener compare by identity and never found the wrapper, so listeners were never removed. once broke the same way because Node's once calls on, so its wrapper was wrapped again and never removed itself. addListener and prependListener were not wrapped and received the handshake message.

The wrapping now covers all five add methods and each wrapper carries a listener property pointing at the caller's function. Node's removeListener and listeners() look through that property, so off and listeners() work without proxying them. once registers a wrapper that removes itself on the first message that is not hidden.

Clean cherry-pick apart from one import conflict. Unit tests and the issue's script pass against the v7 build; the utility process e2e tests pass.