[Form] Deprecated setDefaultOptions() in favor of configureOptions()

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   |  
| Fixed tickets | #12782
| License       | MIT
| Doc PR        | will be provided after approval

This tries to provide a compatible API with the depreciation of the OptionResolverInterface. I would like to have this in 2.6.2 but I think that might not be possible? To me I think we should always provide an API where you do not need to use deprecated classes.

Also can you think of any way to trigger errors on the use of the deprecated setDefaultOptions() method? Since it is usually overwritten without calling the parent class this might be tricky. Maybe only in the resolver if we can check if actual options has been resolved in a call to setDefaultOptions.
This is useless. The Symfony testsuite already requires 4.2+ anyway