Support f16 input for covariance/regr/percentile_cont

[Jefffrey]

Should Float16 be added to NUMERICS at https://github.com/Jefffrey/datafusion/blob/d3630a45272a604f912cbd05ab80de25b7f7c8bc/datafusion/expr-common/src/type_coercion/aggregates.rs#L46 too ?
They are planned for removal but probably should be added until then.

Originally posted by @martin-g in #18647 (comment)