Node type proposal: Retry/Backoff

[sbaker]

Wrap any downstream node or sub-graph with configurable retry logic. Properties: max retries, backoff strategy (fixed, linear, exponential), base delay, max delay, jitter, retry conditions (on error, on specific status codes, on output matching a pattern). Logs each attempt. Different from the errorHandler node which catches and routes errors - this node specifically retries the operation. Essential for resilient workflows that call flaky APIs or rate-limited services.