feat(reactive_stores): add map_untracked to OptionStoreExt

[tqwewe]

Adds an unreactive variant of OptionStoreExt::map called map_untracked.

I didn't add any tests for this, as I'm not entirely sure what to test for.

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On another note, the docs for OptionStoreExt::map state:

will cause it to re-run if the field toggles betwen None and Some(_).

Is this implying it will only be reactive if it changes from None to Some, and will not react to Some(a) -> Some(b) updates to the field? I may be wrong, but from my experience, it seems like it will react regardless if it directly changes between Some and None, and will indeed react to any changes to the field.

[gbj]

Thanks, this looks good. I'm pretty sure that the inaccurate doc there (which implies that Some => Some won't notify) was written earlier on, before I'd figured out how parent/child notification relationships really need to work...

But in fact it seems to me that the behavior that the documentation describes is actually the desired behavior, right? i.e., the map() function here probably should memoize on Some-ness, because if it's Some -> Some the user will catch the change anyway because they're planning to track the subfield?

[tqwewe]

But in fact it seems to me that the behavior that the documentation describes is actually the desired behavior, right?

I've scratched my head for a while, but don't have a good answer for this really. Only thing I'm wondering is, if it did memoize on Some-ness, then what if you wanted to get reactive changes on inner field updates (like what it does currently)? Might be a problem in that case