Default maxCachedWorkflows calculation doesn't account for VM isolate memory being outside V8 heap

[alonp99]

The default maxCachedWorkflows formula uses maxHeapMemory (--max-old-space-size) to calculate
how many workflows to cache. However, workflow VM isolates allocate native memory outside
the V8 heap, not inside it.

This causes unexpected OOMs in containerized environments where:

1. --max-old-space-size is set high (e.g., 4.6GB) relative to container limit (5Gi)
2. Temporal calculates maxCachedWorkflows = ~2600
3. VM isolates consume ~2.6GB of NATIVE memory (not heap)
4. Total memory = heap + VM cache + overhead > container limit → OOMKill

Suggested improvements:

1. Documentation: Warn that VM isolates use native memory, not heap memory
2. Default calculation: Consider using a more conservative default, or factor in
   that VM cache is additive to heap usage
3. Logging: Log a warning if calculated maxCachedWorkflows * ~1MB + maxHeapMemory
   exceeds available system memory

Environment: TypeScript SDK 1.11.7, Node.js 22, Kubernetes