Update `codegen-spec` pkg and add a new edge case OAS

[austinvalle]

• Updates spec package with breaking change to IR JSON output (no breaking change to any go types): https://github.com/hashicorp/terraform-plugin-codegen-spec/pull/29
• Added a new edge case API spec that we can continue to fill out as we go 👍🏻 (custom types for maps, sets, etc.)
  • https://editor-next.swagger.io/ is a nice editor for making changes to OpenAPI specs manually
• Updated the tests to use the JSON output directly instead of the original struct decoding. The error message produced by the struct decoder was not helpful and not really worth the extra code imo.
• Update the make testdata to also use STDOUT for creating the file to match the test
• Removed API specs we aren't currently using for tests

Exact diff after upgrading the package and running make testdata

93a7733c2ee501dc2999eab59d6ee995fabbd6b7

Test failure after updating codegen-spec pkg with binary compare

=== CONT  TestGenerate_WithConfig/Scaleway_-_Instance_API
    /Users/austin.valle/code/terraform-plugin-codegen-openapi/internal/cmd/generate_test.go:67: unexpected difference:   bytes.Join({
                ... // 10 identical lines
                `                                                       "element_type": {`,
                `                                                               "list": {`,
        -       `                                                                       "element_type": {`,
        -       `                                                                               "string": {}`,
        -       `                                                                       }`,
        +       `                                                                       "string": {}`,
                `                                                               }`,
                `                                                       },`,
                ... // 12 identical lines
          }, "\n")

[github-actions[bot]]

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