Refactor some docs examples CSS (#36194)

Refactor some docs examples CSS (#36194)

* Fix some more borders and margins

* Flex utilities docs: remove .bd-highlight class from snippets

* Explicit close target

* Reorder to keep base class up top

* Fix custom position example

* Tooltips: add code snippet, use scss-docs ref for custom tooltip

* Tweak text for pagination examples

* Modals: move custom styles to utilities

* Grid docs: Combine selectors and share coloring

* Refactor tons of little things