feat: add BlockConditional #5578

Job	Run time
check no_std	17s
wasm-unknown	53s
feature-checks	3m 54s
doctest	1m 15s
wasm-wasi	1m 22s
clippy	36s
test ubuntu-latest stable --no-default-features	1m 44s
docs	57s
fmt	12s
test ubuntu-latest stable	1m 23s
test ubuntu-latest stable --all-features	2m 38s
test ubuntu-latest nightly --no-default-features	1m 33s
test ubuntu-latest nightly	1m 11s
test ubuntu-latest nightly --all-features	2m 1s
test ubuntu-latest 1.81 --no-default-features	36s
test ubuntu-latest 1.81	50s
test windows-latest stable --no-default-features	4m 6s
test windows-latest stable	4m 31s
test windows-latest stable --all-features	5m 37s
test windows-latest nightly --no-default-features	4m 21s
test windows-latest nightly	3m 18s
test windows-latest nightly --all-features	5m 52s
test windows-latest 1.81 --no-default-features	2m 9s
test windows-latest 1.81	3m 1s
deny / cargo deny check	19s
ci success	2s
	54m 38s

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