Support type-coercion from Decimal to Float64 (apache#2396)

Can drop this after rebase on commit fe6190b "Support type-coercion from Decimal to Float64 (apache#2396)", first released in 8.0.0
(partially cherry picked from commit fe6190b)

Author: comphead

datafusion/expr/src/type_coercion.rs

@@ -182,6 +182,7 @@ pub fn can_coerce_from(type_into: &DataType, type_from: &DataType) -> bool {
                 | UInt64
                 | Float32
                 | Float64
+                | Decimal(_, _)
         ),
         Timestamp(TimeUnit::Nanosecond, None) => {
             matches!(type_from, Null | Timestamp(_, None) | Date32)