`MastForest` serialization #4899

Job	Run time
rustfmt	46s
Clippy	1m 17s
no-std (stable, wasm32-unknown-unknown)	1m 38s
Check Rust stable on ubuntu with --all-targets --no-default-features	1m 15s
no-std (nightly, wasm32-unknown-unknown)	1m 33s
Check Rust stable on ubuntu with --all-targets	1m 20s
Test Rust stable on ubuntu with --profile test-release	10m 31s
Test Rust nightly on windows-2022	0s
Check Rust stable on ubuntu with --all-targets --all-features	1m 23s
Test Rust stable on ubuntu with --profile test-release --doc	5m 49s
Check Rust nightly on ubuntu with --all-targets --no-default-features	1m 16s
Test Rust nightly on ubuntu with --profile test-release	11m 45s
Check Rust nightly on ubuntu with --all-targets	1m 17s
Test Rust nightly on ubuntu with --profile test-release --doc	6m 23s
Check Rust nightly on ubuntu with --all-targets --all-features	1m 18s
	47m 31s

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