feat: support RANGE in schema

[Linchin]

part of #1724

• add class FieldElementType to support RANGE type in schema
• add related unit tests

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[Linchin]

test failures seem to be api call timeout.

[shollyman]

Probably worth augmenting a system test to create a table with a RANGE type in the schema, but LGTM otherwise.

[Linchin]

@shollyman After adding the system test, I also had to make a bunch of other changes. Please take another look, thank you :)

[shollyman]

Do you also need a setter for this property? Or you're only exposing a setter from the containing type?

[Linchin]

I decided to not allow the element type to be altered in order to protect the table schema from being changed unintentionally. As a reference, most of the properties in class SchemaField don't have setters either.

[shollyman]

Not clear how the changes in this file relate to the feature. Just a side fixup?

[Linchin]

The expected value was changed because the public table somehow lost the first row of the table (id=1) around 12/31, so the system test has been failing.

I have also notified the team managing the public datasets.