[Format] Add more ingest modes

[lidavidm]

We could add more ingest modes to make things easier on integrations like Polars:

https://github.com/pola-rs/polars/blob/702f72a57a1ab2be796679e4facc0d1957a67cc9/py-polars/polars/dataframe/frame.py#L2951-L2955

        if_exists : {'append', 'replace', 'fail'}
            The insert mode.
            'replace' will create a new database table, overwriting an existing one.
            'append' will append to an existing table.
            'fail' will fail if table already exists.

• fail is our CREATE.
• Our append does not create the table; we should document how to do this (try to append, if it fails, try to create).
• replace is not supported.

Polars currently maps replace to CREATE and append to APPEND but this does not match its documented semantics. We should add replace and clarify the documentation.