feat: improve error access logs

[StarpTech]

Motivation and Context

This PR enhances our GraphQL router’s logging and error pipelines, giving you fine-grained control over access-log verbosity, richer diagnostics in both router and subgraph logs, and tidier error propagation.

🎯 What’s Changed

1. Configurable Access-Log Level

   • Now you can set "level" to control which requests get logged ("info" vs "error").

2. Optional Stack Traces

   • The new "add_stacktrace" flag lets you include full stack traces in your access logs when errors occur.

3. New response_error context field

   • This field will log the response errors as JSON array and includes verbose information including stacktraces about all errors.

4. Cleaner Error Composition

   • Resolver errors now propagate intact into the final GraphQL error payload, and we’ve removed an accidental “double join” that was duplicating messages.

---

⚙️ JSON Config Example

access_logs:
  enabled: true
  add_stacktrace: true
  level: error
  router:
    fields:
      - key: "response_error"
        value_from:
          context_field: response_error
  subgraphs:
    enabled: true
    fields:
      - key: "response_error"
        value_from:
          context_field: response_error

In this snippet:

• "level": "error" ensures only failed operations are emitted.
• "add_stacktrace": true" appends the stack trace for any error.
• Field response_error will log the response errors in JSON format including stacktrace information.

---

Related https://github.com/wundergraph/graphql-go-tools/pull/1132

Checklist

• [ ] I have discussed my proposed changes in an issue and have received approval to proceed.
• [ ] I have followed the coding standards of the project.
• [ ] Tests or benchmarks have been added or updated.
• [ ] Documentation has been updated on https://github.com/wundergraph/cosmo-docs.
• [ ] I have read the Contributors Guide.