gen: OptError isn't generated during nested recursion schema with AllOf

[IgorMoiseev1988]

What version of ogen are you using?

$ go list -m github.com/ogen-go/ogen

github.com/ogen-go/ogen v1.14.0

Can this issue be reproduced with the latest version?

Yes

What did you do?

When specification openapi3.0 has nested field with recursive ref into allOf:

      "Error": {
        "type": "object",
        "properties": {
          "code": {
            "type": "string",
            "nullable": true
          },
          "cause": {
            "allOf": [
              {
                "$ref": "#/components/schemas/Error"
              }
            ],
            "nullable": true
          }
        }
      }

then ogen generate structure like this:

type Error struct {
	Code           OptNilString `json:"code"`
	Cause          *OptError    `json:"cause"`
}

But ogen doesn't generate OptError struct, so we have compilation error

If we delete allOf from specification:

      "Error": {
        "type": "object",
        "properties": {
          "code": {
            "type": "string",
            "nullable": true
          },
          "cause": {
            "$ref": "#/components/schemas/Error",
            "nullable": true
          }
        }
      }

Then ogen generates structure like this:

type Error struct {
	Code           OptNilString `json:"code"`
        Cause          *Error       `json:"cause"`
}

and additional generate OptError structure and it's methods

What did you expect to see?

Expected: generation OptError structure is independent of allOf