Allow admin to disable Time Based One-Time Password on user accounts

[mdbitz]

In the plugin you can programmatically disable providers using the filter two_factor_providers
https://github.com/georgestephanis/two-factor/blob/fced6f579161631791c525976a1dbb6211bef35c/class.two-factor-core.php#L85

I'd like to request the ability for Site Admins to disable providers per user. For example the ability to disable the "Time Based One-Time Password" for specific user accounts.

[iandunn]

It seems like the two_factor_enabled_providers_for_user filter would work for this. It was added in #344

I'll go ahead and close this, but we can always reopen it if there's that PR didn't address.

[ocean90]

Created a follow-up since two_factor_enabled_providers_for_user isn't useful for this: #647