[OptionsResolver] Implemented policies for treating unknown/missing options

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | yes
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #7979, replaces #9754
| License       | MIT
| Doc PR        | symfony/symfony-docs#3731

replacement for #10574 which was closed by accident
Not sure. I think since the resolver defines the semantics like required/optional, it makes sense to also do the validation there. How much influence has the overhead? Or do you mean to also remove the validation that was already present?