Automatic merge from submit-queue (batch tested with PRs 47451, 47410, 47598, 47616, 47473)
AWS: Cache instances for ELB to avoid #45050
We maintain a cache of all instances, and we invalidate the cache
whenever we see a new instance. For ELBs that should be sufficient,
because our usage is limited to instance ids and security groups, which
should not change.
Fix#45050
```release-note
AWS: Maintain a cache of all instances, to fix problem with > 200 nodes with ELBs
```
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