[General] Fix DiagonalDirections type (#3795)

## Description

It seems like TypeScript isn't treating an expression where every node
is `const` as `const`:

```ts
const a = 1; // a: 1
const b = 2; // b: 2
const c = a + b; // c: number
```

This caused `DiagonalDirections` type to be a number instead of a union
of consts.

## Test plan

Check the inferred type of `DiagonalDirections`

Author: j-piasecki

packages/react-native-gesture-handler/src/Directions.ts

@@ -3,20 +3,27 @@ const LEFT = 2;
 const UP = 4;
 const DOWN = 8;
 
+// Those need to be constant values rather than expressions for TypeScript not
+// to type them as 'number'.
+const UP_RIGHT = 5; // UP | RIGHT
+const DOWN_RIGHT = 9; // DOWN | RIGHT
+const UP_LEFT = 6; // UP | LEFT
+const DOWN_LEFT = 10; // DOWN | LEFT
+
 // Public interface
 export const Directions = {
-  RIGHT: RIGHT,
-  LEFT: LEFT,
-  UP: UP,
-  DOWN: DOWN,
+  RIGHT,
+  LEFT,
+  UP,
+  DOWN,
 } as const;
 
 // Internal interface
 export const DiagonalDirections = {
-  UP_RIGHT: UP | RIGHT,
-  DOWN_RIGHT: DOWN | RIGHT,
-  UP_LEFT: UP | LEFT,
-  DOWN_LEFT: DOWN | LEFT,
+  UP_RIGHT,
+  DOWN_RIGHT,
+  UP_LEFT,
+  DOWN_LEFT,
 } as const;
 
 // eslint-disable-next-line @typescript-eslint/no-redeclare -- backward compatibility; it can be used as a type and as a value