Update pallet conviction voting to support Block Number Provider #15259

Job	Run time
check-dependency-rules	10s
check-workspace	17s
check-fail-ci	13s
check-markdown	15s
check-readme	3m 6s
preflight / preflight	43s
preflight / ci-versions	1m 1s
check-toml-format	54s
check-umbrella	2m 23s
check-rust-feature-propagation	2m 16s
fmt	1m 9s
test-rust-features	2m 8s
All quick checks passed	1s
	14m 36s

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