arrow

ARROW-11790: [Rust][DataFusion] Change builder signatures to take impl Interator<Item=Expr> rather than &[Expr]

# NOTE:
Since is a fairly major backwards incompatible change (many callsites need to be updated, though mostly mechanically); I gathered some feedback on this approach in https://github.com/apache/arrow/pull/9692 and this is the PR I propose for merge.

I'll leave this open for several days and also send a note to the mailing lists for additional comment

It is part of my overall plan to make the DataFusion optimizer more idiomatic and do much less copying [ARROW-11689](https://issues.apache.org/jira/browse/ARROW-11689)

# Rationale:
All callsites currently need an owned `Vec` (or equivalent) so they can pass in `&[Expr]` and then Datafusion copies all the `Expr`s. Many times the original `Vec<Expr>` is discarded immediately after use (I'll point out where this happens in a few places below). Thus I it would better (more idiomatic and often less copy/faster) to take something that could produce an iterator over Expr

# Changes
1. Change `Dataframe` so it takes `Vec<Expr>` rather than `&[Expr]`
2. Change `LogicalPlanBuilder` so it takes `impl Iterator<Item=Expr>` rather than `&[Expr]`

I couldn't figure out how to allow the `Dataframe` API (which is a Trait) to take an `impl Iterator<Item=Expr>`

Closes #9703 from alamb/alamb/less_copy_in_plan_builder_final

Authored-by: Andrew Lamb <andrew@nerdnetworks.org>
Signed-off-by: Andrew Lamb <andrew@nerdnetworks.org>