Support enhanced timestamp logical types in standardization schema

## Background
Currently, the way we infer the timezone is if the schema's metadata provides a timezone in the timestamp pattern or an additional timezone field. If no such information is provided we assume it is already UTC.

## Feature
It would be helpful to users to make the distinction between `timezoned` and `presumed-UTC` timestamps in the UI.
However, it is important to note that we shouldn't enforce this in the actual schema file as that would make the schemas we use and the actual `SparkStruct` schemas would no longer be compatible.

## Proposed Solution
Once a schema editor is implemented (#31) we can incorporate these two logical types to make it easier for users to provide the proper timezone information.