Add u256 conversions #18757

Job	Run time
build-sway-lib-std	1s
get-fuel-core-version	1s
build-sway-lib-core	1s
build-sway-examples	1s
build-forc-doc-sway-lib-std	1s
build-forc-test-project	1s
build-mdbook	1s
build-reference-examples	1s
cargo-clippy	1s
cargo-build-workspace	1s
forc-fmt-check-panic	1s
forc-fmt-check-sway-examples	1s
forc-fmt-check-sway-lib-core	1s
forc-fmt-check-sway-lib-std	1s
cargo-fmt-check	1s
cargo-run-e2e-test-midenvm	1s
cargo-run-e2e-test-evm	1s
cargo-test-lib-std	1s
cargo-test-sway-lsp	1s
cargo-test-workspace	1s
cargo-toml-fmt-check	1s
cargo-unused-deps-check	1s
forc-pkg-fuels-deps-check	1s
forc-run-benchmarks	1s
forc-unit-tests	1s
pre-publish-check	0s
cargo-run-e2e-test	1s
cargo-run-e2e-test-release	1s
cargo-test-forc-debug	1s
build-publish-master-image	1s
notify-slack-on-failure	1s
publish	1s
build-publish-release-image	1s
Build and upload forc binaries to release	1s
	33s

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