Add statistics methods to TableProvider trait for use in cost-based optimizations in the logical plan

[andygrove]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
For projects like Dask SQL that use DataFusion for logical query planning and optimization, I would like to support cost-based optimizations in the logical plan. The first step in enabling this is to allow Dask SQL's TableProvider to provide statistics about tables (such as estimated row count and column statistics - min, max, num nulls, num distinct).

Describe the solution you'd like
I would like the ability to access table statistics from the TableProvider trait.

Describe alternatives you've considered
None

Additional context
None