This refactors styles/native.css to:

• Remove extraneous custom properties
• Add #region markers for collapsible sections
• Consolidate redundant/overlapping rules
• Add --wa-content-spacing for easier content flow customization
• Move out styles that were designed for the code blocks in our docs

Additionally, this:

• Fixes some theme overrides.css styles that were styling native elements with the now removed custom properties
• Fixes incorrect spacing in drawer and dialog