Filter Unneeded SnapshotInfo Instances Early in TransportGetSnapshotsAction (#78032) (#79321)

Better to filter as early as possible to release the memory asap and not even fetch things we don't need to fetch to begin with.
There's still a bunch of spots remaining where similar optimizations can be added quickly before we implement the system index for the remaining searching/fetching that we can't easily exclude up-front.
This already gives vastly improved performance for many requests though for obvious reasons.

Author: original-brownbear