PF6 Design guideline updates

[andrew-ronaldson]

This Epic captures the updates required for the PFv6 updates. Most of this work will be updating screenshots but there are also some documented CSS variables.

### Component guideline updates
- [ ] Guideline updates: About modal
- [ ] Guideline updates: Accordions
- [ ] Guideline updates: Action list
- [ ] Guideline updates: Alert
- [ ] Guideline updates: Avatar
- [ ] Guideline updates: Banner
- [ ] Guideline updates: Breadcrumb
- [ ] https://github.com/patternfly/patternfly-org/issues/4274
- [ ] https://github.com/patternfly/patternfly-org/issues/4275
- [ ] Guideline updates: Copy clipboard
- [ ] Guideline updates: Code block & Code editor
- [ ] Guideline updates: List,  Simple list, Data list & Decription list
- [ ] Guideline updates: Calendar month
- [ ] Guideline updates: Divider
- [ ] Guideline updates: Drag and drop
- [ ] Guideline updates: Drawer
- [ ] Guideline updates: Dual list selector
- [ ] Guideline updates: Empty state
- [ ] Guideline updates: Expandable section
- [ ] Guideline updates: File uploads
- [ ] Guideline updates: Form elements
- [ ] Guideline updates: Hint
- [ ] Guideline updates: Inline edit
- [ ] Guideline updates: Input group & Text input groups
- [ ] Guideline updates: Jump links
- [ ] Guideline updates: Label
- [ ] Guideline updates: Login page
- [ ] Guideline updates: Masthead
- [ ] Guideline updates: Menu, Select, dropdown & Menu toggle
- [ ] Guideline updates: Modal
- [ ] Guideline updates: Navigation
- [ ] Guideline updates: Notification badge (stateful button) & Notification drawer
- [ ] Guideline updates: Number inputs
- [ ] Guideline updates: Overflow menu
- [ ] https://github.com/patternfly/patternfly-org/issues/4273
- [ ] Guideline updates: Pagination
- [ ] Guideline updates: Panel
- [ ] Guideline updates: Password strength
- [ ] Guideline updates: Popover & Tooltips
- [ ] Guideline updates: Progress & Progress stepper
- [ ] Guideline updates: Search input
- [ ] Guideline updates: Sidebar
- [ ] Guideline updates: Slider
- [ ] Guideline updates: Table
- [ ] Guideline updates: Tabs
- [ ] Guideline updates: Timestamp
- [ ] Guideline updates: Toggle group
- [ ] Guideline updates: Toolbar
- [ ] Guideline updates: Treeview
- [ ] Guideline updates: Truncate
- [ ] Guideline updates: Wizard