add(book): Adds a section on Regtest usage to the Zebra book #1329

Job	Run time
Generate crates matrix	11s
Check crates matrix	3s
Build zebrad crate	35m 42s
Build zebra-utils crate	18m 10s
Build zebra-test crate	1m 33s
Build zebra-state crate	22m 27s
Build zebra-script crate	4m 35s
Build zebra-scan crate	21m 4s
Build zebra-rpc crate	24m 1s
Build zebra-node-services crate	3m 22s
Build zebra-network crate	6m 57s
Build zebra-grpc crate	14m 42s
Build zebra-consensus crate	19m 9s
Build zebra-chain crate	4m 59s
Build tower-fallback crate	1m 2s
Build tower-batch-control crate	1m 18s
Open or update issues for building crates individually failures	0s
	2h 59m 15s

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