Convert GLFM examples from old GM approach

What does this MR do and why?

Related: Tracking Issue: Implement GLFM scripts per the ... (#361241 - closed)

Moves all GitLab Flavored Markdown Examples from old "Golden Master" based approach to the new snapshot-based approach.

Examples were moved from:

1. spec/fixtures/markdown/markdown_golden_master_examples.yml
2. ee/spec/fixtures/markdown/markdown_golden_master_examples.yml

...into:

1. glfm_specification/input/gitlab_flavored_markdown/glfm_internal_extensions.md

References

See the GLFM Specification Guide development documentation for much more context on all of this work: https://docs.gitlab.com/ee/development/gitlab_flavored_markdown/specification_guide

How to set up and validate locally

As long as CI is green, it should be ok, but you can do the following:

1. Run scripts/glfm/run-snapshot-tests.sh and ensure all the specs it runs work.
   • Note: It appears this didn't trigger the relevant backend and frontend tests to run in the CI pipeline. This has been captured in a follow up task here: #361241 (closed)
   • For now, pipeline:run-all-jest and pipeline:run-all-rspec have been added to ensure tests are passing.
2. Run scripts/glfm/update-specification.rb and scripts/glfm/update-example-snapshots.rb and ensure there are no changes to any generated GLFM files
3. Ensure there are no occurrences of Error - check implementation in glfm_specification/output_example_snapshots/html.yml or other output files.
   • Note: These should really probably fail the script. Added a follow-up task to implement this here: #361241 (closed)

Helper script

I wrote the following script (but did not commit) to help with the conversion. Pasting here for future reference:

scripts/glfm/migrate-from-golden-master.rb:

#!/usr/bin/env ruby
# frozen_string_literal: true

require_relative '../lib/glfm/migrate_from_golden_master'
Glfm::MigrateFromGoldenMaster.new.process

scripts/lib/glfm/migrate_from_golden_master.rb:

# frozen_string_literal: true
require 'yaml'

module Glfm
  class MigrateFromGoldenMaster
    def process
      gm_examples_path = Pathname.new(
        File.expand_path("../../../spec/fixtures/markdown/markdown_golden_master_examples.yml", __dir__)
      )

      ee_gm_examples_path = Pathname.new(
        File.expand_path("../../../ee/spec/fixtures/markdown/markdown_golden_master_examples.yml", __dir__)
      )

      rendered_html_hash = YAML.safe_load(File.open(gm_examples_path), symbolize_names: true, aliases: true)
      ee_rendered_html_hash = YAML.safe_load(File.open(ee_gm_examples_path), symbolize_names: true, aliases: true)

      print_examples(rendered_html_hash)
      print_examples(ee_rendered_html_hash)
    end

    private

    def print_examples(rendered_html_hash)
      rendered_html_hash.each do |example|
        name = example.fetch(:name)
        markdown = example[:markdown]
        html = example[:html]

        puts <<~MARKDOWN

          ### #{name}

          ```````````````````````````````` example gitlab
          #{markdown}
          .
          TODO: Write canonical HTML for this example
          ````````````````````````````````
        MARKDOWN
      end
    end
  end
end

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.