feat: ability to login with email, username or both (#7086)

`auth.loginWithUsername`:

```ts
auth: {
  loginWithUsername: {
    allowEmailLogin: true, // default: false
    requireEmail: false, // default: false
  }
}
```

#### `allowEmailLogin`
This property will allow you to determine if users should be able to
login with either email or username. If set to `false`, the default
value, then users will only be able to login with usernames when using
the `loginWithUsername` property.

#### `requireEmail`
Require that users also provide emails when using usernames.

test/auth/payload-types.ts

@@ -207,6 +207,6 @@ export interface Auth {
 
 
 declare module 'payload' {
-  // @ts-ignore 
+  // @ts-ignore
   export interface GeneratedTypes extends Config {}
-}
+}