Polling API additions proposal

Under discussion. The proposal extends the polling surface with weak handles, socket handles, generic timer/signal/process/notification handles, and priority events.

The weak-handle design addresses event loops unintentionally keeping resources alive. The broader handle set provides integration points for the related IO hooks work. These are proposed changes: a description in an RFC is not evidence of release availability.

Recheck the primary page for current scope, status and ballots. No vote result is inferred here.

Related: IO hooks, array shorthand.