Fix socket connection cancellation deadlock

[heoblitz]

Summary

Fix a deadlock between socket completion and task cancellation by resuming continuations outside NSLock.

Changelog

Fix occasional connection hangs.

Test Plan

• Local: forced race passed 10/10; Swift tests passed (Mac 267, SDK 166, consumer 2).
• CI: 20 Mac test runs and simulator E2E passed. Final commit only removes temporary diagnostics.