fix(data-warehouse): Fixed reading unix timestamps in a TZ-aware way

[Gilbert09]

Problem

• We had duplicate days when plotting Stripe data in product analytics due to the way we were parsing unix timestamps from data warehouse

Changes

• Use the timezone-aware function of toDateTime when reading unix timestamps for Stripe and other integration data

Does this work well for both Cloud and self-hosted?

• Yes

How did you test this code?

• Via browser clicky clicks