Introduce `MastForestStore` #4869

Job	Run time
Clippy	1m 16s
rustfmt	15s
no-std (stable, wasm32-unknown-unknown)	1m 35s
Check Rust stable on ubuntu with --all-targets --no-default-features	1m 13s
no-std (nightly, wasm32-unknown-unknown)	1m 36s
Test Rust nightly on windows-2022	0s
Check Rust stable on ubuntu with --all-targets	1m 22s
Test Rust stable on ubuntu with --profile test-release	11m 5s
Check Rust stable on ubuntu with --all-targets --all-features	1m 21s
Test Rust stable on ubuntu with --profile test-release --doc	6m 12s
Check Rust nightly on ubuntu with --all-targets --no-default-features	1m 13s
Test Rust nightly on ubuntu with --profile test-release	11m 2s
Check Rust nightly on ubuntu with --all-targets	1m 30s
Test Rust nightly on ubuntu with --profile test-release --doc	5m 53s
Check Rust nightly on ubuntu with --all-targets --all-features	1m 19s
	46m 52s

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