[FEA] Support cast from string to timestamp for non-UTC timezones.

[revans2]

Is your feature request related to a problem? Please describe.
This depends on #6835 and possibly on more. The issue here is that we need to parse a string to a timestamp in a different time zone. But we already don't really support parsing timestamps correctly as is. This is disabled by default. We require the year to be a full 4 digit year. We don't support all of the formats that cast does and we don't support parsing the time in a different timezone.

Hopefully we can just reuse the existing code and then convert the result to UTC using #6831 but we are going to have to do a lot of testing to see if that works. This might require that we write a custom kernel to do some of this. We might need to write a custom kernel at some point soon anyways to speed up timestamp parsing and to allow us to parse out time zones that could be included per string.

This is a fundamentally different problem than the other ones that pull out a part of a value from a timestamp. This is why it is a stand alone issue.