Promotions should use timezone in shop settings for time calculations not server time

[brent-hoover]

Time zone is set here in the shop settings

I think this probably only involves changing const now = new Date() to something like const now = new Date().toLocaleString("en-US", { timeZone: "America/Chicago" }); where "America/Chicago" would be the timezone from ShopSettings. And probably want to define that function globally and maybe cache the timezone.

[brent-hoover]

This should use the getShopTimeZones util that I added for state. I was thinking that we could just use state for the query but I think the addition of #6668 means that we need to have more flexibility in how we query based on time. We should think about that as we build this.

[vanpho93]

FE transformed input dates into UTC before sending to server so we don't need to convert before using.