refactor: move ChainUpdate to a separate file #1187

Job	Run time
Database Migration	9m 34s
Backward Compatibility	17m 37s
Protobuf Backward Compatibility	11s
Cargo Nextest (Linux)	17m 16s
Genesis Changes	9m 12s
Cargo Nextest (Linux Nightly)	16m 46s
Sanity Checks	6m 2s
Cargo Nextest (MacOS)	16m 45s
Cargo Audit	24s
Lychee Lints	11s
Style	35s
Upgradability	10m 56s
RPC Schema	6m 16s
Upload Coverage	24s
	1h 52m 9s

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