Add type+format mappings for Go generator

Description

Adds support for explicit type+format mappings in the Go generator, allowing precise control over numeric types through both integer and number formats. This enhancement enables users to specify exact Go numeric types using OpenAPI's type and format fields.

New Type Mappings

Integer Format Mappings

Number Format Mappings

Default mappings remain unchanged:

• integer → int32
• number → float32
• long → int64
• float → float32
• double → float64
• decimal → float64

Usage Example

components:
  schemas:
    MyModel:
      type: object
      properties:
        byteValue:
          type: integer
          format: uint8
        preciseFloat:
          type: number
          format: float64
        standardInt:
          type: integer  # defaults to int32

Closes: #21031

@antihax (2017/11) @grokify (2018/07) @kemokemo (2018/09) @jirikuncar (2021/01) @ph4r5h4d (2021/04) @lwj5 (2023/04)

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in Git BASH)
  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• File the PR against the correct branch: master (upcoming 7.x.0 minor release - breaking changes with fallbacks), 8.0.x (breaking changes without fallbacks)
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.