Introduce `GlobalVar` akin to `LocalVar` and introduce `get_global` instruction similar to `get_local`. #23373

Job	Run time
build-sway-lib-std	48s
build-sway-lib-core	58s
get-fuel-core-version	32s
build-reference-examples	1m 13s
build-sway-examples	51s
forc-fmt-check-panic	1m 55s
forc-fmt-check-sway-examples	43s
forc-fmt-check-sway-lib-core	45s
forc-fmt-check-sway-lib-std	1m 5s
build-forc-doc-sway-lib-std	1m 23s
build-forc-test-project	4m 24s
build-mdbook	5m 48s
cargo-build-workspace	2m 24s
cargo-clippy	48s
cargo-fmt-check	10s
cargo-toml-fmt-check	14s
check-sdk-harness-test-suite-compatibility	32s
cargo-run-e2e-test-evm	6m 22s
cargo-test-forc	1m 40s
cargo-test-lib-std	6m 8s
cargo-test-sway-lsp	6m 21s
cargo-test-workspace	4m 51s
forc-pkg-fuels-deps-check	15s
cargo-unused-deps-check	2m 46s
forc-run-benchmarks	3m 32s
forc-unit-tests	5m 44s
pre-publish-check	0s
cargo-run-e2e-test-release	5m 43s
cargo-test-forc-client	3m 39s
cargo-test-forc-debug	2m 43s
cargo-run-e2e-test	5m 38s
cargo-test-forc-node	1m 19s
build-publish-master-image	1s
notify-slack-on-failure	1s
publish	1s
build-publish-release-image	1s
verifications-complete	1s
Build and upload forc binaries to release	1s
	1h 21m 20s

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