feat: add XOR type definition W-18851777

[shetzel]

Adds a new XOR type definition so that we can define types that behave like this:

interface A { name: string; }
interface B { id: string; }

type MyXORType = XOR<A, B>;

const valid1: MyXORType = { name: 'My_Foo' }; // Valid
const valid2: MyXORType = { id: '0xT0000cxxxeeRGtHM' };    // Valid

const invalid1: MyXORType = { name: 'My_Foo', id:'0xT0000cxxxeeRGtHM' }; // Error: Object literal may only specify known properties
const invalid2: MyXORType = {}; // Error: Property 'name' or 'id' is missing

@W-18851777@