Gap Sync: Skip Body Requests for Non-Archive Nodes

[lrubasze]

Summary

This PR optimizes gap sync bandwidth usage by skipping body requests for non-archive nodes. Bodies are unnecessary during gap sync when the node doesn't maintain full block history, while archive nodes continue to request bodies to preserve complete history.
It reduces bandwidth consumption and database size significantly for typical validator/full nodes.

Additionally added some gap sync statistics for observability:

• Introduced GapSyncStats to track bandwidth usage: header bytes, body bytes, justification bytes
• Logged on gap sync completion to provide visibility into bandwidth savings

[lrubasze]

/cmd prdoc --audience node_dev --audience node_operator --bump patch --force

[skunert]

Overall logic looks quite good. Ome thing you can do is make this behaviour a bit more explicit by adding a node to the warp sync CLI. Just a quick mention so that users can know what state the node will be in when warp sync is finished.

[bkontur]

cc: @karolk91 maybe it looks like something related what we discussed the last week?

[lrubasze]

/cmd prdoc --audience node_dev --audience node_operator --bump patch --force

[paritytech-workflow-stopper]

All GitHub workflows were cancelled due to failure one of the required jobs.
Failed workflow url: https://github.com/paritytech/polkadot-sdk/actions/runs/20956214511
Failed job name: test-linux-stable-int

[iulianbarbu]

lgtm!

[karolk91]

cc: @karolk91 maybe it looks like something related what we discussed the last week?

looks related indeed, @lrubasze can we hold a bit with merge of this ? I will be soon exploring how warp syncing related to bulletin parachain works..

but my current understanding is that this is a case when we have block pruning set but still need BODY of the blocks during gap sync -- for sure we don't need the full history of blocks with BODY-ies, just the last X blocks defined by the retention period of the chain

also possible that I'm mixing here the concept of relay chain warp syncing and parachain warp syncing

[bkchr]

Some last nits.

[lrubasze]

/cmd fmt