[Maintenance]: StringList and StrPropList need classes of their own

[bubblobill]

Describe the problem

For users using macros, StrPropLists and StringLists do not play well with others.
StrPropLists fail when nested particularly with other StrPropLists, rendering their key-value pairs inaccessible.
Gson does not convert them properly to JSON beyond the first iteration.

The improvement you'd like to see

Each should have its own class, being a simple wrapper for either a List or Map.
With classes of their own, Gson has a better chance of serialising and deserialising them in depth.
Writing specific (de)serialisers will ensure better handling if necessary.

Expected Benefits

Improved input and output integrity.
Better user experience.

Additional Context

No response

[cwisniew]

String lists and props are broken and sadly due to creating compatibility issues are probably unfixable.

The advice for the longest time has been use json. It's less fragile and a lot faster, as well as having many utility functions not available to string lists and props. Everyone who tried to fix str lists/props failed.