Update GroupingChooser with local model for transient UI state

[haynesjm42]

Fixes #3398

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[haynesjm42]

This is duplicated in the mobile component - didn't want to export this model but not sure how we can share it between the 2 packages ... should we just export and put a comment as "Not for application use"?

[lbwexler]

you can put it in an /impl directory, and mark it as @internal. We do this all the time!

[haynesjm42]

Thanks for the tip, I knew we must have a pattern for this (and do this all the time in apps). Was hoping for something that would hide the class to app code, doesn't seem like there is any enforcement of @internal . Looks like there are lots of proposals out there for this kind of thing, hopefully something makes it in eventually.

Looks like there is a way to strip these from d.ts output - https://www.typescriptlang.org/tsconfig#stripInternal - though since we are full typescript I don't think this does anything.

[lbwexler]

same as above

[haynesjm42]

Suggesting to move this into a shared impl directory? Can't really do that unfortunately as it's child components use platform-specific components

[lbwexler]

discussed with John -- there was a misunderstanding -- just mean that we should be passing the state down to the local components as dimensionList({imodel: impl}). That way they have typed access to everything.