Determine local timezone on client instead of server

[jonmmease]

Currently, calculations that involve converting the stored UTC time to Local time are performed according to the server's timezone. Instead, this timezone should be determined by the client.

As a new architecture, the client should provide its named timezone as part of the task graph query. Then we can use chrono-tz on the server to convert from UTC to the local time zone. For hashing, it might be easier to add the timezone to each transform/expression that needs it, and then include the timezone string in the hash of expression/transform.