Add `EnumVariant` parsed decl and minor refactors to namespace-related code #19800

Job	Run time
build-sway-examples	1m 35s
build-sway-lib-core	4m 56s
build-sway-lib-std	1m 23s
get-fuel-core-version	46s
build-forc-doc-sway-lib-std	2m 0s
build-forc-test-project	5m 54s
build-reference-examples	1m 29s
check-sdk-harness-test-suite-compatibility	45s
forc-fmt-check-panic	1m 55s
forc-fmt-check-sway-examples	59s
forc-fmt-check-sway-lib-std	1m 8s
forc-fmt-check-sway-lib-core	1m 10s
build-mdbook	5m 56s
cargo-build-workspace	3m 44s
cargo-clippy	1m 1s
cargo-fmt-check	15s
cargo-run-e2e-test-evm	4m 47s
cargo-run-e2e-test-midenvm	2m 41s
cargo-test-lib-std	2m 52s
cargo-test-sway-lsp	5m 29s
cargo-test-workspace	5m 33s
cargo-toml-fmt-check	13s
cargo-unused-deps-check	4m 29s
forc-pkg-fuels-deps-check	15s
forc-run-benchmarks	3m 53s
pre-publish-check	0s
forc-unit-tests	1m 45s
cargo-run-e2e-test-release	14m 2s
cargo-run-e2e-test	12m 49s
cargo-test-forc-debug	4m 12s
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
	1h 37m 57s

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