[slang-netlist] Refactor handling of variable references with selectors #1457

Job	Run time
bindings	12m 15s
build (clang-sanitize, ubuntu-22.04)	9m 9s
conan	1m 16s
build (gcc-release, ubuntu-22.04)	3m 5s
build (gcc-11-release, ubuntu-22.04)	2m 50s
build (gcc-debug-shared, ubuntu-22.04)	2m 39s
build (gcc-debug-noexcept, ubuntu-22.04)	3m 14s
build (macos-release, macos-13)	1m 35s
build (win64-release, windows-latest)	4m 3s
linux-coverage	3m 3s
build (win64-debug-shared, windows-latest)	3m 52s
build (win64-debug-noexcept, windows-latest)	3m 34s
	50m 35s

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