Sync variants

[ben-rogerson]

This PR contains a bunch of changes to sync the variants a little more closely with tailwind latest.

This included moving the variant definitions into corePlugins.js so they can now be found right next to the class definitions.

Task list

• [x] Sync variant config with tailwindcss
• [x] Support customizing class name when using darkMode: 'class' (#5800)
• [x] Add enabled variant (#7905)
• [x] Add backdrop variant (#7924, #8526)
• [x] Add prefers-contrast media query variants (#8410)
• [x] Add optional variant (#8486)
• [x] Error when registering an invalid custom variant (#8345)

Not variants

Twin now automatically generates a full set of reversed not- variants from the list of pseudoVariants:

// Positional
tw`not-first:block`
tw`not-last:block`
tw`not-only:block`
tw`not-odd:block`
tw`not-even:block`
tw`not-first-of-type:block`
tw`not-last-of-type:block`
tw`not-only-of-type:block`

// State
tw`not-visited:block`
tw`not-target:block`
tw`not-open:block`

// Forms
tw`not-default:block`
tw`not-checked:block`
tw`not-indeterminate:block`
tw`not-placeholder-shown:block`
tw`not-autofill:block`
tw`not-optional:block`
tw`not-required:block`
tw`not-valid:block`
tw`not-invalid:block`
tw`not-in-range:block`
tw`not-out-of-range:block`
tw`not-read-only:block`

// Content
tw`not-empty:block`

// Interactive
tw`not-focus-within:block`
tw`not-hover:block`
tw`not-focus:block`
tw`not-focus-visible:block`
tw`not-active:block`
tw`not-enabled:block`
tw`not-disabled:block`

// Twin custom
tw`not-all:block`
tw`not-all-child:block`
tw`not-sibling:block`
tw`not-hocus:block`
tw`not-link:block`
tw`not-read-write:block`
tw`not-svg:block`
tw`not-even-of-type:block`
tw`not-odd-of-type:block`

// These `not-` classes also apply to the `group-not-` and `peer-not-` class sets:
tw`group-not-first:block`
tw`peer-not-first:block`