Expose optional `num_centroids` argument in `approx_percentile_cont`'s fluent API

[Michael-J-Ward]

Is your feature request related to a problem or challenge?

approx_percentile_cont's fluent API currently exposes expression and percentile.

datafusion/datafusion/functions-aggregate/src/approx_percentile_cont.rs

Lines 49 to 55 in 1ecdf90

	make_udaf_expr_and_func!(
	ApproxPercentileCont,
	approx_percentile_cont,
	expression percentile,
	"Computes the approximate percentile continuous of a set of numbers",
	approx_percentile_cont_udaf
	);

However, as described in the datafusion docs, the UDAF accepts a 3rd optional argument, an integer number of centroids for T-Digest

datafusion/datafusion/functions-aggregate/src/approx_percentile_cont.rs

Lines 76 to 94 in 1ecdf90

	impl ApproxPercentileCont {
	/// Create a new [`ApproxPercentileCont`] aggregate function.
	pub fn new() -> Self {
	let mut variants = Vec::with_capacity(NUMERICS.len() * (INTEGERS.len() + 1));
	// Accept any numeric value paired with a float64 percentile
	for num in NUMERICS {
	variants.push(TypeSignature::Exact(vec![num.clone(), DataType::Float64]));
	// Additionally accept an integer number of centroids for T-Digest
	for int in INTEGERS {
	variants.push(TypeSignature::Exact(vec![
	num.clone(),
	DataType::Float64,
	int.clone(),
	]))
	}
	}
	Self {
	signature: Signature::one_of(variants, Volatility::Immutable),
	}

Describe the solution you'd like

Consistent with exposing optional arguments for array_slice and regexp_* fluent apis, add a 3rd optional argument to approx_percentile_cont's fluent API.

Describe alternatives you've considered

No response

Additional context

I'll have a PR for this shortly.