Add as_u256 for U128 #23438

Job	Run time
build-mdbook	7m 43s
build-forc-test-project	4m 11s
build-forc-doc-sway-lib-std	1m 25s
build-reference-examples	1m 9s
build-sway-examples	1m 54s
build-sway-lib-std	49s
build-sway-lib-core	1m 13s
cargo-build-workspace	1m 46s
cargo-clippy	50s
cargo-fmt-check	11s
cargo-run-e2e-test-evm	4m 28s
cargo-test-forc	1m 42s
cargo-test-sway-lsp	8m 46s
cargo-test-workspace	5m 27s
cargo-toml-fmt-check	13s
cargo-unused-deps-check	5m 37s
cargo-test-lib-std	11m 11s
check-sdk-harness-test-suite-compatibility	29s
forc-fmt-check-panic	2m 2s
forc-fmt-check-sway-examples	42s
forc-fmt-check-sway-lib-core	1m 1s
forc-pkg-fuels-deps-check	38s
forc-fmt-check-sway-lib-std	1m 5s
forc-run-benchmarks	4m 5s
forc-unit-tests	8m 27s
get-fuel-core-version	32s
pre-publish-check	0s
cargo-test-forc-client	3m 43s
cargo-run-e2e-test-release	15m 1s
cargo-run-e2e-test	14m 13s
cargo-test-forc-debug	2m 15s
cargo-test-forc-node	1m 19s
notify-slack-on-failure	1s
build-publish-master-image	0s
publish	0s
build-publish-release-image	0s
Build and upload forc binaries to release	0s
verifications-complete	0s
	1h 54m 8s

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