Move filter predicate to join conversion to optimization rule

[Dandandan]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
Currently, finding out the implicit join predicates in a WHERE clause is done in converting.
In order to remove cross joins from the plan, we should move this logic to an optimization rule.

Describe the solution you'd like
Add a new optimization rule that looks for expressions in the form col1 = col2 AND col3 = col4 in the WHERE clause and changes the plan to join on those (instead of a cross join).
The existing code can be removed (and create a cross join in the first step).

Describe alternatives you've considered
N/a.

Additional context
n/a

[alamb]

I believe this is now done, specifically in https://github.com/apache/datafusion/blob/main/datafusion/optimizer/src/extract_equijoin_predicate.rs