Introduce `GlobalVar` akin to `LocalVar` and introduce `get_global` instruction similar to `get_local`. #23332

Job	Run time
build-sway-lib-core	2m 41s
build-sway-lib-std	2m 18s
get-fuel-core-version	32s
build-reference-examples	2m 41s
build-sway-examples	4m 6s
forc-fmt-check-sway-lib-core	2m 39s
forc-fmt-check-sway-lib-std	2m 28s
build-forc-doc-sway-lib-std	3m 23s
build-forc-test-project	3m 5s
build-mdbook	6m 13s
cargo-build-workspace	4m 25s
cargo-clippy	2m 24s
check-sdk-harness-test-suite-compatibility	32s
forc-fmt-check-panic	3m 38s
forc-fmt-check-sway-examples	2m 21s
cargo-fmt-check	18s
cargo-run-e2e-test-evm	5m 25s
cargo-test-forc	7m 37s
cargo-test-lib-std	7m 29s
cargo-test-sway-lsp	8m 3s
cargo-toml-fmt-check	16s
forc-pkg-fuels-deps-check	25s
forc-run-benchmarks	3m 52s
forc-unit-tests	8m 14s
cargo-test-workspace	8m 13s
cargo-unused-deps-check	7m 12s
pre-publish-check	0s
cargo-test-forc-client	9m 51s
cargo-run-e2e-test-release	14m 6s
cargo-test-forc-debug	3m 6s
cargo-run-e2e-test	13m 29s
build-publish-master-image	0s
notify-slack-on-failure	0s
publish	0s
build-publish-release-image	0s
Build and upload forc binaries to release	0s
verifications-complete	0s
	2h 21m 2s

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