typescript-operations: Missing types with a nested fragment when exportFragmentSpreadSubTypes and skipTypename are enabled

**Describe the bug**
When both `exportFragmentSpreadSubTypes` and `skipTypename` are `true`, some types are not generated when a fragment has certain nested objects.

**To Reproduce**
Reproduction here: https://codesandbox.io/s/great-noyce-wdyut
Missing types are shown in the `no-undef` lint errrors.

1. My GraphQL schema:

```graphql
interface BlockInterface {
uid: String
title: String
}

type Root_BlockType implements BlockInterface {
uid: String
title: String
children: [BlockInterface]
}
type Child_BlockType implements BlockInterface {
uid: String
title: String
children: [BlockInterface]
}

type FragmentOne_Type implements BlockInterface {
uid: String
title: String
}
type FragmentTwo_Type implements BlockInterface {
uid: String
title: String
}
type FragmentThree_Type implements BlockInterface {
uid: String
title: String
}

union Blocks = Root_BlockType | Child_BlockType

type Result implements BlockInterface {
uid: String
title: String
blocks: Blocks
}

type Query {
search: BlockInterface
}
```

2. My GraphQL operations:

```graphql
fragment RootBlockFields on Root_BlockType {
__typename
uid
}

fragment RootChildren on BlockInterface {
...FragmentOne
...FragmentTwo
}

fragment RootBlock on Root_BlockType {
...RootBlockFields

children {
...RootChildren
...ChildBlock
}
}

fragment ChildChildren on BlockInterface {
...FragmentOne
...FragmentTwo
...FragmentThree
}

fragment ChildBlock on Child_BlockType {
__typename
uid

children {
...ChildChildren

...on Root_BlockType {
...RootChildren

children {
...on Child_BlockType {
__typename
uid

children {
...ChildChildren
}
}
}
}
}
}

fragment FragmentOne on FragmentOne_Type {
__typename
uid
}

fragment FragmentTwo on FragmentTwo_Type {
__typename
uid
title
}

fragment FragmentThree on FragmentThree_Type {
__typename
uid
title
}

query SampleQuery {
search {
...on Result {
__typename

blocks {
...RootBlock
}
}
}
}

```

3. My `codegen.yml` config file:

```yml
schema: schema.graphql
documents: document.graphql
generates:
types.ts:
plugins:
- typescript
- typescript-operations
config:
exportFragmentSpreadSubTypes: true
skipTypename: true
```

**Expected behavior**
All types should be generated. Instead, the generated operation types reference the following types that are not defined:
- `RootChildren_Root_BlockType_Fragment`
- `RootChildren_Child_BlockType_Fragment`
- `RootChildren_FragmentThree_Type_Fragment`
- `RootChildren_Result_Fragment`
- `ChildChildren_Root_BlockType_Fragment`
- `ChildChildren_Child_BlockType_Fragment`
- `ChildChildren_Result_Fragment`

**Environment:**

- OS: MacOS
- `@graphql-codegen/...`: 1.17.10
- `@graphql-codegen/typescript-operations`: 1.17.8
- NodeJS: 12.15

**Additional context**