upgrade to polkadot sdk 1.12 (#371) #791

Job	Run time
build	25m 21s
Cancel Previous Runs	3s
Build Runtimes (encointer-node-notee)	12m 37s
build-try-runtime-and-benchmarks	25m 33s
cargo-toml-fmt	5s
Rust check +nightly fmt --all -- --check (x86_64-unknown-linux-gnu)	48s
Rust check clippy -p encointer-client-notee (x86_64-unknown-linux-gnu)	10m 15s
unit-tests	20m 17s
test_bootstrap_demo_community.sh	21m 51s
test_bot_community.sh	7m 45s
test_register_business.sh	2m 10s
Draft Release	0s
Publish Runtimes	0s
	2h 6m 45s

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