chore: migrate snapshot and backup docs, remove unused #13031

Job	Run time
Build MacOS	3m 26s
Build Ubuntu	7m 22s
cargo-publish-dry-run	7m 12s
Calibnet check	3m 55s
Forest CLI checks	7m 44s
Snapshot export checks	12m 23s
Calibnet no discovery checks	7m 14s
Calibnet stateless RPC check	11s
Calibnet stateless mode check	1m 26s
Wallet tests	5m 23s
State migrations	4m 52s
Bootstrap checks - Forest	4m 0s
Bootstrap checks - Lotus	4m 8s
Calibnet eth mapping check	5m 52s
Calibnet kademlia checks	4m 15s
db-migration-checks	2m 23s
Calibnet RPC checks	18m 13s
Devnet checks	5m 37s
Devnet Curio checks	0s
Calibnet snapshot parity checks	0s
Integration tests status	1s
	1h 45m 37s

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