Rust

WIP: Rework block notification #239

Job	Run time
build	4m 16s
linting	5s
cross-testing (stable, ubuntu-latest)	1m 39s
cross-testing (stable, windows-latest)	1m 21s
cross-testing (stable, macos-latest)	1m 45s
cross-testing (nightly, ubuntu-latest)	1m 39s
cross-testing (nightly, windows-latest)	1m 26s
cross-testing (nightly, macos-latest)	1m 42s
cross-testing (1.64, ubuntu-latest)	1m 41s
cross-testing (1.64, windows-latest)	1m 29s
cross-testing (1.64, macos-latest)	1m 23s
	18m 26s

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