made a _Numerical DataType

Both `Int` and `Float` inherit from it.

src/fastcs/datatypes.py

@@ -22,31 +22,32 @@ def dtype(self) -> type[T]:  # Using property due to lack of Generic ClassVars
         pass
 
 
-@dataclass(frozen=True)
-class Int(DataType[int]):
-    """`DataType` mapping to builtin ``int``."""
+T_Numerical = TypeVar("T_Numerical", int, float)
+
 
+@dataclass(frozen=True)
+class _Numerical(DataType[T_Numerical]):
     units: str | None = None
     min: int | None = None
     max: int | None = None
     min_alarm: int | None = None
     max_alarm: int | None = None
 
+
+@dataclass(frozen=True)
+class Int(_Numerical[int]):
+    """`DataType` mapping to builtin ``int``."""
+
     @property
     def dtype(self) -> type[int]:
         return int
 
 
 @dataclass(frozen=True)
-class Float(DataType[float]):
+class Float(_Numerical[float]):
     """`DataType` mapping to builtin ``float``."""
 
     prec: int = 2
-    units: str | None = None
-    min: float | None = None
-    max: float | None = None
-    min_alarm: float | None = None
-    max_alarm: float | None = None
 
     @property
     def dtype(self) -> type[float]: