[Rust][DataFusion] Rename ExpressionVisitor --> ExprVisitor and standardize input

[asfimport]

Rename ExpressionVisitor ExprVisitor for consistency and change it to use &mut self rather than consuming the visitor for consistency with PlanVisitor (as well as the soon to be created ExprVisitor

Reporter: Andrew Lamb / @alamb
Assignee: Andrew Lamb / @alamb

_{Note: This issue was originally created as ARROW-11711. Please see the migration documentation for further details.}

[asfimport]

Andrew Lamb / @alamb:
Migrated to github: apache/datafusion#181