[Form] Moved auto_initialize option to the BaseType

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #8162
| License       | MIT
| Doc PR        | -

I'm not fully confident in this change, so let someone review it first please. My thinking was - since "auto_initialized" option is always passed to a form factory, it should be required by the base type.