Improve & unify validation in LogicalPlan::with_new_exprs (apache#12264)

* Improve & unify validation in LogicalPlan::with_new_exprs

When adding new plan node type, `LogicalPlan::with_new_exprs` needs to
be updated. Different code branches apply different inputs validation
style (no validation, just assert, or assert with messages), so it's
unclear which code pattern to follow.  This commit unifies the
validation and adds it to the branches where there was none.

* #inline

* rename and return Result

* Add doc line