Introduce `GlobalVar` akin to `LocalVar` and introduce `get_global` instruction similar to `get_local`. #23375

Job	Run time
build-forc-test-project	4m 46s
build-forc-doc-sway-lib-std	2m 4s
build-mdbook	8m 43s
build-reference-examples	1m 1s
build-sway-examples	1m 9s
build-sway-lib-core	51s
build-sway-lib-std	1m 5s
cargo-build-workspace	2m 5s
cargo-clippy	54s
cargo-fmt-check	15s
cargo-run-e2e-test-evm	5m 32s
cargo-test-forc	2m 16s
cargo-test-lib-std	7m 21s
cargo-test-sway-lsp	7m 42s
cargo-test-workspace	5m 5s
cargo-toml-fmt-check	16s
cargo-unused-deps-check	2m 52s
check-sdk-harness-test-suite-compatibility	28s
forc-fmt-check-panic	1m 49s
forc-fmt-check-sway-examples	1m 10s
forc-fmt-check-sway-lib-core	56s
forc-fmt-check-sway-lib-std	56s
forc-pkg-fuels-deps-check	15s
forc-run-benchmarks	3m 33s
forc-unit-tests	7m 58s
get-fuel-core-version	36s
pre-publish-check	0s
cargo-test-forc-client	3m 0s
cargo-run-e2e-test	11m 23s
cargo-test-forc-debug	3m 20s
cargo-run-e2e-test-release	18m 10s
cargo-test-forc-node	1m 20s
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 48m 52s

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