Introduce `GlobalVar` akin to `LocalVar` and introduce `get_global` instruction similar to `get_local`. #23370

Job	Run time
build-sway-lib-core	53s
build-sway-lib-std	1m 12s
get-fuel-core-version	29s
build-reference-examples	1m 2s
build-sway-examples	1m 33s
forc-fmt-check-sway-examples	48s
forc-fmt-check-sway-lib-core	52s
forc-fmt-check-sway-lib-std	1m 5s
build-forc-doc-sway-lib-std	1m 46s
build-forc-test-project	4m 2s
build-mdbook	5m 46s
cargo-build-workspace	2m 27s
cargo-run-e2e-test-evm	5m 26s
cargo-clippy	54s
cargo-test-lib-std	6m 14s
cargo-fmt-check	10s
cargo-toml-fmt-check	16s
check-sdk-harness-test-suite-compatibility	26s
forc-fmt-check-panic	1m 44s
cargo-test-forc	2m 23s
cargo-test-sway-lsp	8m 58s
cargo-test-workspace	5m 41s
cargo-unused-deps-check	3m 31s
forc-pkg-fuels-deps-check	22s
forc-run-benchmarks	2m 29s
forc-unit-tests	6m 49s
pre-publish-check	0s
cargo-test-forc-debug	2m 44s
cargo-run-e2e-test-release	13m 41s
cargo-run-e2e-test	13m 32s
cargo-test-forc-client	2m 46s
cargo-test-forc-node	1m 13s
notify-slack-on-failure	1s
publish	0s
build-publish-master-image	0s
build-publish-release-image	0s
Build and upload forc binaries to release	0s
verifications-complete	0s
	1h 41m 15s

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