API to get Expr's type and nullability without a DFSchema

[alamb]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
I am trying to implement (fast) expression simplification that sits on the critical IOx query path (as the predicates get simplified and then used to prune out chunks based on catalog statistics)

When i created a PR to use the API proposed in #1717 for simplify exprs, I found out that to get is_boolean_type() and nullable information from an Expr I needed to pass it a DFSchema (which is a kind of wrapper over a normal Arrow Schema). For us in IOx this involves a copy (as we have our own wrapper over Schema).

Describe the solution you'd like
I would like to be able to use expression simplification without creating a new DFSchema.

Specifically

1. Add a trait that can provide the needed information for schema quries to Expr
2. Change the functions on Expr that take a &DFSchema such as Expr::nullable to be nullable
3. impl this new trait for DFSchema so that existing callsites work

Describe alternatives you've considered
N/A

Additional context
You can see the code here: https://github.com/influxdata/influxdb_iox/pull/3588/files#r796004295