Pause pruning during snapshotting

[ordian]

Fixes #7863.

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[rphmeier]

I think the problem isn't that simple, because we'll end up accumulating a ton of pending state data in memory while we aren't pruning.

[ordian]

@rphmeier How about tracking the earliest state era needed for taking a snapshot?

[rphmeier]

can you elaborate? I don't understand what you mean exactly

[ordian]

ordian> I was thinking we can track and constantly update the minimal block number needed to produce the current state chunk. Or we can't do that?
rphmeier> in general it will always be the same block
rphmeier> otherwise we would have to add a ton of metadata to each trie node saying the block number it was last modified
rphmeier> that would be possible if we had an actual "trie" DB which is specialized for storing the state trie