Add new rule to validate pattern directory structure

[shatakshiiii]

SUMMARY

This PR adds a new rule pattern for validating a sample pattern directory structure within an ansible collection.

Pattern rule consists of following sub-rules -

• pattern[missing-readme]- triggers when the README.md file is missing from a pattern directory.
• pattern[missing-meta] - triggers when a pattern.json spec file exists but parent meta directory is missing.
• pattern[missing-playbook] - triggers when either the required playbooks directory or playbook file is missing.
• pattern[name-mismatch] - triggers when pattern name does not matches with the name key in pattern.json file.

Steps to validate pattern dir structure -

• Scaffold a pattern to an existing collection using ansible-creator -
  ansible-creator add resource pattern sample_pattern path/to/coll_proj
• Navigate to the collection directory - cd coll_proj
• Run ansible-lint on the pattern definition meta file -
  ansible-lint extensions/patterns/sample_pattern/meta/pattern.json
• Review the validation results.

Fixes: #4665
Fixes: AAP-47360

[alisonlhart]

🚀

[samccann]

Since the draft spec talks about 64 character limit to the pattern name and characters allowed, should this PR also validate that as well?

[shatakshiiii]

Since the draft spec talks about 64 character limit to the pattern name and characters allowed, should this PR also validate that as well?

There is a function in ansible-creator that validates pattern name early on during the scaffolding of pattern. I did not added same logic here in lint thinking it would be redundant.

As per my understanding - User will first use ansible-creator to scaffold a pattern (where if pattern name does not follow the spec then it will fail right there). Then use ansible-lint to validate the same pattern.

Looking for your thoughts here @samccann @ssbarnea @alisonlhart !