Remove `Min`/`Max` references from `AggregateExec::get_minmax_descr`

[alamb]

Is your feature request related to a problem or challenge?

Part of #11151 (where we are removing special case uses of Min/Max)

Describe the solution you'd like

Remove the code here:

datafusion/datafusion/physical-plan/src/aggregates/mod.rs

Lines 485 to 494 in f58df32

	pub fn get_minmax_desc(&self) -> Option<(Field, bool)> {
	let agg_expr = self.aggr_expr.iter().exactly_one().ok()?;
	if let Some(max) = agg_expr.as_any().downcast_ref::<Max>() {
	Some((max.field().ok()?, true))
	} else if let Some(min) = agg_expr.as_any().downcast_ref::<Min>() {
	Some((min.field().ok()?, false))
	} else {
	None
	}
	}

Specifically, the idea is to remove the pattern

       expr.as_any().downcast_ref::<Max>()

and

       expr.as_any().downcast_ref::<Min>()

Describe alternatives you've considered

Perhaps we can add function like this to AggregteExpr and implement it for Min and Max:

impl AggregateExpr {
    /// If this function is max, return (output_field, true)
    /// if the function is min, return (output_field, false)
    /// otherwise return None (the default)
    ///
    /// output_field is the name of the column produced by this aggregate
    ///
    /// Note: this is used to use special aggregate implementations in certain conditions
    pub fn get_min_max(&self) -> Option<(Field, bool)> { None }
...
}

Additional context

No response

[Rachelint]

take