Impl setting a custom LdapAuthenticationProvider w/ AbstractLdapAuthenticationManagerFactory

[Haarolean]

Hi,

I suggested some adjustments within #11448, but as nobody replied I decided to raise a PR.

Additionally,

1. I've considered the approach of adding a property like useActiveDirectoryComponents, but since ActiveDirectoryLdapAuthenticationProvider would require additional params (like a domain name) it doesn't look applicable. So I rejected this approach.
2. Since LdapAuthoritiesPopulator is not applicable to ActiveDirectoryLdapAuthenticationProvider (or AbstractLdapAuthenticationProvider generally), the code looks like it does. This might be changed after ActiveDirectoryLdapAuthenticationProvider does not support different AuthoritiesPopulator #4490 is implemented.

Let me know what you think.
Cheers

[jzheaux]

Thanks, @Haarolean. I'm going to close this PR at this point since providing the full authentication provider could instead be done with new ProviderManager(authenticationProvider). Let's please continue discussing on #11448 as needed.