Refactor away usage of `NUMERICS`/`INTEGERS` in `datafusion/expr-common/src/type_coercion/aggregates.rs`

[Jefffrey]

datafusion/datafusion/expr-common/src/type_coercion/aggregates.rs

Lines 44 to 66 in 264030c

	pub static INTEGERS: &[DataType] = &[
	DataType::Int8,
	DataType::Int16,
	DataType::Int32,
	DataType::Int64,
	DataType::UInt8,
	DataType::UInt16,
	DataType::UInt32,
	DataType::UInt64,
	];
	pub static NUMERICS: &[DataType] = &[
	DataType::Int8,
	DataType::Int16,
	DataType::Int32,
	DataType::Int64,
	DataType::UInt8,
	DataType::UInt16,
	DataType::UInt32,
	DataType::UInt64,
	DataType::Float32,
	DataType::Float64,
	];

Refactor these away in favour of using the TypeSignature API: https://github.com/apache/datafusion/blob/264030cca76d0bdb4d8809f252b422e72624a345/datafusion/expr-common/src/signature.rs

Need to take care for functions that will be affected, especially as for NUMERICS it doesn't contain Float16 or Decimals which TypeSignature::Numeric does include. Consider what changes might be necessary for downstream functions.