feat(optimistic_block): Introduce the optimistic block struct #9457

Job	Run time
Backward Compatibility	11m 32s
Protobuf Backward Compatibility	9s
Cargo Nextest (Linux)	10m 18s
Cargo Fmt	23s
Cargo Nextest (Linux Nightly)	13m 1s
Protocol Schema	13m 18s
Database Migration	11m 41s
Genesis Changes	9m 46s
Sanity Checks	6m 12s
Style	34s
Upgradability	11m 26s
Cargo Audit	20s
Cargo Deny	32s
Cargo Clippy	8m 55s
Non-default Configuration Builds	1m 16s
Themis	36s
Unused Dependencies	6m 55s
Rust Doctests	11m 3s
Cargo check publishable packages separately (Linux, linux, ubuntu-latest)	8m 9s
Cargo check publishable packages separately (Windows, win, windows-latest)	2m 17s
Generate Coverage Artifact (unit, unit)	2m 44s
Upload Coverage	17s
	2h 11m 24s

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