Remove SIMULATE_CHOOSER_COLUMNS memory hacks and expose global constants in utility expressions #1198

Job	Run time
linux-64-py	6m 15s
Estimation Mode Unit Tests	17m 56s
Estimation Notebooks Test	50m 13s
win-64	15m 41s
macOS	9m 58s
placeholder_multiple_zone	7m 15s
random_seed_generation_test	3m 1s
Expression Profiling Tests	7m 48s
prototype_mwcog	56m 42s
Standard 1-Zone Example (MTC)	21m 54s
estimation_edb_creation_test	6m 36s
prototype_mtc	54m 54s
prototype_mtc_extended	41m 19s
placeholder_psrc	56m 35s
Standard 2-Zone Example (SANDAG)	36m 19s
production_semcog	7m 6s
develop-docbuild	0s
	6h 39m 32s

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