Get rid of globals in various functions

As discussed with @MichelJuillard, we should try to get rid of globals in

• stoch_simul
• simult_

as most of their callers and subsequently called functions already use local instances of the variables

added enhancement label

assigned to @houtanb

mentioned in commit preprocessor@04b6a68a

closed via commit e043c609

Reopening to create compatibility layer for stoch_simul, simult_, and discretionary_policy following discussions on the dev list and mattermost

reopened

closing to track compatibility issues in #1656 (closed)

closed

mentioned in issue #1656 (closed)