`LocalChain` with hardwired genesis block #4319

Job	Run time
Check WASM	37s
Build and test (stable, true, --no-default-features)	1m 56s
Rust fmt	6s
Check no_std	26s
Build and test (stable, true, --all-features)	2m 12s
clippy_check	29s
Build and test (1.57.0, --no-default-features)	2m 25s
Build and test (1.57.0, --all-features)	3m 22s
	11m 33s

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