[DataType] Add is_integer and is_signed queries (#110)

These queries could be convenient for conditional checks in ONNX Script
pattern rewrite rules. A simple example would be rewriting subtraction
of a constant as addition of the negative (additive inverse) of the
constant which should be restricted to signed numbers (as unsigned
numbers do not have an additive inverse - at least within their data
type bounds). See #109

---------

Signed-off-by: Christoph Berganski <christoph.berganski@gmail.com>
Signed-off-by: Justin Chu <justinchuby@users.noreply.github.com>
Co-authored-by: Justin Chu <justinchuby@users.noreply.github.com>

Author: iksnagreb

src/onnx_ir/_enums.py

@@ -169,6 +169,42 @@ def is_floating_point(self) -> bool:
             DataType.FLOAT4E2M1,
         }
 
+    def is_integer(self) -> bool:
+        """Returns True if the data type is an integer."""
+        return self in {
+            DataType.UINT8,
+            DataType.INT8,
+            DataType.UINT16,
+            DataType.INT16,
+            DataType.INT32,
+            DataType.INT64,
+            DataType.UINT32,
+            DataType.UINT64,
+            DataType.UINT4,
+            DataType.INT4,
+        }
+
+    def is_signed(self) -> bool:
+        """Returns True if the data type is a signed type."""
+        return self in {
+            DataType.FLOAT,
+            DataType.INT8,
+            DataType.INT16,
+            DataType.INT32,
+            DataType.INT64,
+            DataType.FLOAT16,
+            DataType.DOUBLE,
+            DataType.COMPLEX64,
+            DataType.COMPLEX128,
+            DataType.BFLOAT16,
+            DataType.FLOAT8E4M3FN,
+            DataType.FLOAT8E4M3FNUZ,
+            DataType.FLOAT8E5M2,
+            DataType.FLOAT8E5M2FNUZ,
+            DataType.INT4,
+            DataType.FLOAT4E2M1,
+        }
+
     def __repr__(self) -> str:
         return self.name