poc(scanner): get started with the blockchain scanner proof of concept #63

Job	Run time
Generate crates matrix	14s
Check crates matrix	3s
Build tower-batch-control crate	31s
Build tower-fallback crate	32s
Build zebra-chain crate	2m 57s
Build zebra-consensus crate	13m 6s
Build zebra-network crate	3m 55s
Build zebra-node-services crate	2m 45s
Build zebra-rpc crate	13m 5s
Build zebra-scanner crate	14m 30s
Build zebra-script crate	2m 23s
Build zebra-state crate	11m 50s
Build zebra-test crate	1m 34s
Build zebra-utils crate	16m 41s
Build zebrad crate	23m 53s
Open or update issues for building crates individually failures	0s
	1h 47m 59s

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