feat: add CSS theming variables for focused & hover elements

[brandyscarney]

Feature Request

Ionic version:
master

Branch created with the beginning of the non-breaking changes: https://github.com/ionic-team/ionic/tree/non-breaking-button-states

Describe the Feature Request
Add hover, focused, activated state to missing button components.

The following pull request made some major changes to the way we set hover, activated & focused: #19440

This allows users to customize the button by changing the color once and not having to know the opacity of each state. That change only applied to components with existing hover states due to it being breaking, the following need to be added:

Name	Existing Hover (master)	Updated Hover?	Updated Activated?	Updated Focused?
Alert (Buttons)	⬜	⬜	⬜	⬜
Card	⬜	⬜	⬜	⬜
Checkbox	⬜	⬜	⬜	⬜
Chip	⬜	⬜	⬜	⬜
Item Option	⬜	✅	⬜	⬜
Picker (Buttons)	⬜	✅	⬜	⬜
Radio	⬜	⬜	⬜	⬜
Tab Button	⬜	⬜	⬜	✅
Toast (Buttons)	⬜	⬜	⬜	⬜
Toggle	⬜	⬜	⬜	⬜

• Alert needs hovers on the buttons and tappable items
• Router link is just an anchor, should it have an underline or follow MD design for clear buttons?
• Buttons (in overlays) should be named --button-background-hover

Activated Components

Components that have --background-activated & --color-activated or --button-background-activated & --button-color-activated for overlays.

• action-sheet (MISSING --button-color-activated)
• button
• fab-button
• item

Hover Components

Components that have --background-hover & --color-hover or --button-background-hover & --button-color-hover for overlays.

• action-sheet
• back-button
• button
• fab-button
• item-option (MISSING --color-hover)
• item
• menu-button
• picker (MISSING --button-color-hover)
• segment-button

Focused Components

Components that have --background-focused & --color-focused or --button-background-focused & --button-color-focused for overlays.

• back-button
• button
• fab-button
• item
• menu-button
• tab-button (MISSING --color-focused)