Implements bitfocus/companion-module-base#118

This has turned out to be a more complex state machine than I initially expected, so I am wondering if this should be held back for 4.1 (it could still be reverted in the module lib, so that the other changes can be released)

This api change is done so that how the options are stored can be different from how they are used, without needing modules to be the ones doing the parsing.

This is a precursor to #2345, which I expect will build on this by further by changing the structure of the options object that companion and upgrade scripts use, but not for action/feedback execution or subscribe/unsubscribe calls.
At this stage, that means we can pre-parse variables in textinput fields (only those with the useVariables flag set for now) before passing the objects off to the modules.

This should be non-breaking for modules, and only those using the updated base lib will hit the new flows, so any bugs found will have limited impact.

TODO

• try it with a module
• thoroughly test it with a module
• write some unit tests?