Function delegatedTransportHandler

Drives a transport operation over the best available transport for a node.

Iterates the node's ESPRMNeoNode.transportOrder and, for each mode present in ESPRMNeoNode.availableTransports:

1. For the local mode, validates a baseUrl is known and enriches the transport config metadata with the node's securityType/pop/username.
2. Uses a registered custom transport manager for that mode if one exists; otherwise constructs the built-in ESPTransportManager.
3. Runs the supplied operation against the transport. The first success wins; failures fall through to the next mode in the order.

Must be invoked bound to a node, e.g. delegatedTransportHandler.call(node, (m) => m.setParam(payload, node)).