Rework the documentation to incorporate the Ruff formatter (#7732)

## Summary

This PR updates our documentation for the upcoming formatter release.

Broadly, the documentation is now structured as follows:

- Overview
- Tutorial
- Installing Ruff
- The Ruff Linter
    - Overview
    - `ruff check`
    - Rule selection
    - Error suppression
    - Exit codes
- The Ruff Formatter
    - Overview
    - `ruff format`
    - Philosophy
    - Configuration
    - Format suppression
    - Exit codes
    - Black compatibility
        - Known deviations
- Configuring Ruff
    - pyproject.toml
    - File discovery
    - Configuration discovery
    - CLI
    - Shell autocompletion
- Preview
- Rules
- Settings
- Integrations
    - `pre-commit`
    - VS Code
    - LSP
    - PyCharm
    - GitHub Actions
- FAQ
- Contributing

The major changes include:

- Removing the "Usage" section from the docs, and instead folding that
information into "Integrations" and the new Linter and Formatter
sections.
- Breaking up "Configuration" into "Configuring Ruff" (for generic
configuration), and new Linter- and Formatter-specific sections.
- Updating all example configurations to use `[tool.ruff.lint]` and
`[tool.ruff.format]`.

My suggestion is to pull and build the docs locally, and review by
reading them in the browser rather than trying to parse all the code
changes.

Closes https://github.com/astral-sh/ruff/issues/7235.

Closes https://github.com/astral-sh/ruff/issues/7647.

mkdocs.template.yml

@@ -61,6 +61,7 @@ extra_css:
   - stylesheets/extra.css
 not_in_nav: |
   /rules/*
+  /formatter/*
 extra:
   analytics:
     provider: fathom