Introduce `GlobalVar` akin to `LocalVar` and introduce `get_global` instruction similar to `get_local`. #23454

Job	Run time
build-sway-lib-core	44s
get-fuel-core-version	36s
build-reference-examples	1m 0s
build-sway-examples	1m 8s
build-sway-lib-std	48s
forc-fmt-check-sway-lib-core	54s
check-sdk-harness-test-suite-compatibility	35s
forc-fmt-check-sway-examples	48s
forc-fmt-check-panic	1m 50s
forc-fmt-check-sway-lib-std	40s
build-forc-test-project	4m 32s
build-mdbook	7m 14s
build-forc-doc-sway-lib-std	1m 16s
cargo-build-workspace	2m 1s
cargo-clippy	34s
cargo-fmt-check	11s
cargo-run-e2e-test-evm	7m 31s
cargo-toml-fmt-check	14s
cargo-test-lib-std	8m 34s
cargo-test-forc	1m 32s
cargo-test-sway-lsp	9m 7s
cargo-test-workspace	5m 35s
cargo-unused-deps-check	6m 54s
forc-pkg-fuels-deps-check	18s
forc-run-benchmarks	2m 54s
forc-unit-tests	5m 40s
pre-publish-check	0s
cargo-run-e2e-test-release	13m 20s
cargo-test-forc-node	58s
cargo-test-forc-debug	2m 41s
cargo-test-forc-client	3m 35s
cargo-run-e2e-test	13m 35s
notify-slack-on-failure	0s
build-publish-master-image	0s
publish	0s
verifications-complete	0s
build-publish-release-image	0s
Build and upload forc binaries to release	0s
	1h 47m 19s

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