consensus: make `Header` blob fees u64 #4199

Job	Run time
wasm-unknown	37s
test ubuntu-latest stable --no-default-features	1m 12s
check no_std	20s
cfg-check	24s
clippy	35s
test ubuntu-latest stable	1m 36s
test ubuntu-latest stable --all-features	2m 11s
docs	1m 25s
doctest	1m 1s
feature-checks	3m 5s
test ubuntu-latest nightly --no-default-features	1m 10s
test ubuntu-latest nightly	1m 11s
fmt	14s
wasm-wasi	1m 6s
test ubuntu-latest nightly --all-features	1m 58s
test ubuntu-latest 1.79 --no-default-features	29s
test ubuntu-latest 1.79	49s
test windows-latest stable --no-default-features	4m 37s
test windows-latest stable	4m 39s
test windows-latest stable --all-features	5m 21s
test windows-latest nightly --no-default-features	4m 2s
test windows-latest nightly	3m 50s
test windows-latest nightly --all-features	4m 24s
test windows-latest 1.79 --no-default-features	2m 35s
test windows-latest 1.79	2m 36s
	51m 27s

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