Durable function support

[willfarrell]

Brain dump from re:invent

• split core into buffered, stream, durable. All with abort signal (will be very useful for durable)
• durable doesn’t support stream response, add docs that http responses shout use websocket or server side events (app sync?)
• add new middleware to save event/internal/response/error to state plus new middleware to resolve all internal state (see Otel logger pattern)

Other

• update context to include tenant
• updste docs around concurrent runs and how to write safe middleware
• update type source to be official AWS new