[DOCS] Restructure chapters - further alignment

[wiwaszko-intel]

📝 Description

Restructure SceneScape documentation:

• adjust toc in index
• move release-notes.md to the main menu and update to align with the current OEP release notes template
• adjust get-started.md: add child prerequisites.md
• create how-to-guides.md and child directory grouping guides ("Build a Scene", "Camera Calibration", and articles previously grouped under "Using SceneScape")

Does not yet change "Additional Resources" and "Other Topics".

✨ Type of Change

Select the type of change your PR introduces:

• 🐞 Bug fix – Non-breaking change which fixes an issue
• 🚀 New feature – Non-breaking change which adds functionality
• 🔨 Refactor – Non-breaking change which refactors the code base
• 💥 Breaking change – Changes that break existing functionality
• 📚 Documentation update
• 🔒 Security update
• 🧪 Tests
• 🚂 CI

🧪 Testing Scenarios

Describe how the changes were tested and how reviewers can test them too:

• ✅ Tested manually
• 🤖 Ran automated end-to-end tests

✅ Checklist

Before submitting the PR, ensure the following:

• 🔍 PR title is clear and descriptive
• 📝 For internal contributors: If applicable, include the JIRA ticket number (e.g., ITEP-123456) in the PR title. Do not include full URLs
• 💬 I have commented my code, especially in hard-to-understand areas
• 📄 I have made corresponding changes to the documentation
• ✅ I have added tests that prove my fix is effective or my feature works