Organize ExampleGroup methods into a logical order.
Refactor example group aliasing.

- Bring it in line with how example and
  shared example aliasing work.
- Improve the docs.
Remove `:focused` metadata.

It's a bit silly to double up with `:focused` and `:focus`.

This still needs a 2.99 deprecation.
Add fspecify and fexample for parity with fit.
Provide doc groupings.
Merge pull request #1413 from rspec/code-audit-changes-part-4

Code audit changes part 4