docs: reorganize documentation and remove stale CI configs

[Sunny6889]

What does this PR do?

Consolidates the project's documentation under docs/ with consistent lower-case names, adds a README Documentation index linking every guide, marks two outdated protocol copies as superseded, adds Super-Representative private-key security notes to the config guide, removes two unused CI configs (.codeclimate.yml, sonar-project.properties), and .dockerignore file.

Why are these changes required?

• Several guides existed but were unlinked from the README — readers had no entry point.
• METRICS_CHANGELOG.md and the protobuf protocol doc lived outside docs/, cluttering the repo root and the proto tree.
• Two 2022-era protocol copies gave no hint they were stale, risking readers trusting the wrong file.
• The config guide never warned that a plaintext block-producing key can leak via file permissions or be committed to Git.
• .codeclimate.yml / sonar-project.properties are no longer used by CI.

This PR has been tested by:

• Unit Tests — N/A (docs + config-file removal only; no code paths touched)
• Manual Testing — verified all moved paths resolve and every README/cross-doc link is correct

Follow up

None.

Extra details

[abn2357]

Two issues and one optional naming nit as below, please consider whether modifications are required.:

• Reconcile the remaining Sonar references

  This PR removes .codeclimate.yml and sonar-project.properties because they are no longer used by CI, but Sonar-related references remain:

  • framework/build.gradle:3 still applies org.sonarqube.
  • CONTRIBUTING.md:150 says that the Sonar scanner is automatically triggered for pull requests.
  • CONTRIBUTING.md:161 requires contributions to pass the Sonar scanner test.

  Please update CONTRIBUTING.md to reflect the current CI process.

• Fix the relative source link after moving the metrics changelog

  After moving METRICS_CHANGELOG.md into docs/, the link to common/src/main/java/org/tron/common/prometheus/ on line 22 now resolves to the non-existent path:

  docs/common/src/main/java/org/tron/common/prometheus/

  Please change the link target from:

  common/src/main/java/org/tron/common/prometheus/

  to:

  ../common/src/main/java/org/tron/common/prometheus/

• [Nit] Consider using kebab-case consistently

  Most files under docs/ use kebab-case, while metrics_changelog.md uses snake_case. Consider renaming it to metrics-changelog.md for consistency with names such as protobuf-protocol-document.md.

[Sunny6889]

Two issues and one optional naming nit as below, please consider whether modifications are required.:

• Reconcile the remaining Sonar references
  This PR removes .codeclimate.yml and sonar-project.properties because they are no longer used by CI, but Sonar-related references remain:

  • framework/build.gradle:3 still applies org.sonarqube.
  • CONTRIBUTING.md:150 says that the Sonar scanner is automatically triggered for pull requests.
  • CONTRIBUTING.md:161 requires contributions to pass the Sonar scanner test.

  Please update CONTRIBUTING.md to reflect the current CI process.

• Fix the relative source link after moving the metrics changelog
  After moving METRICS_CHANGELOG.md into docs/, the link to common/src/main/java/org/tron/common/prometheus/ on line 22 now resolves to the non-existent path:
  docs/common/src/main/java/org/tron/common/prometheus/
  Please change the link target from:
  common/src/main/java/org/tron/common/prometheus/
  to:
  ../common/src/main/java/org/tron/common/prometheus/

• [Nit] Consider using kebab-case consistently
  Most files under docs/ use kebab-case, while metrics_changelog.md uses snake_case. Consider renaming it to metrics-changelog.md for consistency with names such as protobuf-protocol-document.md.

very good suggestion, will fix all.