feat: add shared response types tracking infrastructure

[devin-ai-integration]

📝 Description

This PR implements the first step of a feature to allow shared response types in the GraphQL Kotlin client generator. Currently, the system generates duplicate classes for the same GraphQL type when it appears in different operations. This change adds the infrastructure to track and identify response types that are shared across multiple operations.

Key Changes:

• Added tracking infrastructure: New responseClassToTypeSpecs map in GraphQLClientGeneratorContext to track response types, similar to existing enum and input type tracking
• Implemented shared type detection: New detectSharedResponseTypes() method that analyzes all operation contexts to identify types used across multiple operations
• Extended shared types system: Response types are now included in the sharedTypes collection alongside enums, input types, and scalar converters
• Refactored generation flow: Updated the main generate() method to collect contexts from all operations before processing shared types

Important Notes:

• This is explicitly the "first step" - actual deduplication logic is not implemented yet
• The infrastructure identifies shared types but doesn't yet prevent duplicate class generation
• Future work will involve implementing the logic to actually use shared types instead of generating per-operation duplicates

Testing:

• All existing tests pass (63 tests, 0 failures)
• ktlint and detekt checks pass with 0 code smells

Key Areas for Review:

1. Shared type detection logic: Verify the detectSharedResponseTypes() method correctly identifies types used across multiple operations
2. Performance implications: The new detection processes all contexts and type specs - assess impact on large codebases
3. Integration patterns: Ensure the response type tracking follows the same patterns as existing enum/input type sharing
4. Edge cases: Consider polymorphic types, complex selection sets, and other GraphQL type scenarios
5. Refactoring safety: Verify the generateWithContext() refactoring maintains existing behavior

🔗 Related Issues

This implements the first step toward resolving duplicate class generation for GraphQL response types across operations, as requested by @akkp-windsurf.

Link to Devin run: https://app.devin.ai/sessions/355a9ae4e762480a804152127e6e1f92
Requested by: Arthur Poon (@akkp-windsurf)

[devin-ai-integration]

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