Align Return Types of no-arg and Customizer arg Configuration Methods

It is a common way to configure Spring Security like this:

http.formLogin();
http.httpBasic();

Where each configuration is in its own line, this is quite a reasonable alternative and there are many users who prefer this way to chaining methods.

With the deprecation of .and() and the non-lambda methods (see #12629), and, therefore, the removal in 7.0, users will be forced to use:

http.formLogin(Customizer.withDefaults());
http.httpBasic(Customizer.withDefaults());

The above configuration does not give any advantage over the former. We should consider replacing the deprecated methods with a variant that returns the root builder object, for example, HttpSecurity.

public HttpSecurity httpBasic() {
    // ...
}

Some methods, like oauth2ResourceServer, maybe should not return HttpSecurity since it doesn't make sense to configure it without the additional .jwt() or .opaqueToken() methods.

Start by reviewing the no-argument and Customizer-argument configuration methods described in this issue, along with the deprecation context in #12629. Determine which methods should return HttpSecurity and which, such as oauth2ResourceServer, should retain a specialized return type; done means the return types are consistent without losing supported configuration paths.