Support Ibis Backend

[cosmicBboy]

Is your feature request related to a problem? Please describe.

Pandera currently doesn't support validating data in a persistent datastore (e.g. MySQL, Postgres, etc). It would benefit users to be able to write pandera schemas that can then be compiled to a query language (like SQL), executed on a remote DB, that either:

1. validates the data in-place, returning an error report if the data is invalid
2. validates the data and load it into memory using some framework (e.g. pandas) for further processing

A high-leverage integration to enable this behavior would be with ibis, a data analytics framework that hooks into various backends (duckdb, mysql, postgres, etc).

Describe the solution you'd like

For the MVP integration with ibis:

• Implement a schema specification for ibis
• Implement a backend validator for ibis
• Support writing custom checks

Describe alternatives you've considered NA