You are tasked with implementing a failover mechanism for executing tasks across multiple distributed nodes. Each node has a priority level, and you need to ensure tasks are executed reliably even when some nodes fail. Your task is to implement the ExecuteWithFailover function that:

Tries nodes in order of priority (lowest number first)
If a node fails, immediately tries the next node without waiting
If a node doesn't respond within 500ms, tries the next node but keeps the original request running
Returns the first successful result, or all errors if all nodes fail
Properly handles context cancellation throughout the process

Tags Concurrency Context Failover