feat(consensus): Isthmus Network Upgrade Txs #1341

Job	Run time
docs	18s
cfg-check	17s
doctest	53s
clippy	58s
examples	11s
feature-checks	2m 45s
feature-powerset	3m 37s
fmt	12s
no-std	45s
wasm-unknown	57s
test stable --no-default-features	1m 1s
wasm-wasi	43s
test stable	1m 0s
test stable --all-features	1m 24s
test nightly --no-default-features	41s
test nightly	38s
test nightly --all-features	58s
test 1.81 --no-default-features	1m 3s
test 1.81	59s
	19m 20s

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