Use openid profile email as the default scope value [SDK-2926]

[Widcket]

Changes

⚠️ THIS PR CONTAINS BREAKING CHANGES

The library was using an assortment of different values as the default value of the scope parameter in Authentication client methods and Web Auth. The default scope value used across the library was changed to openid profile email, with the exception of the renew(withRefreshToken:scope:) method, in which it remains nil.

As the scope parameter in Authentication client methods have a default value, it is not necessary for that parameter to be optional. So it was changed to be non-optional.

Finally, in a couple of Authentication client methods, the scope and audience parameters switched places for the sake of consistency with the rest of the methods.

Testing

• This change adds unit test coverage
• This change has been tested on the latest version of the platform/language or why not

Checklist

• I have read the Auth0 general contribution guidelines
• All existing and new tests complete without errors
• All active GitHub checks have passed

[Widcket]

With a default value, there's no point in having the scope parameter be optional.