Tile: add experimental variant

[aagonzales]

Original discussion issue reference: #11351

This issue is to close out the exploratory work Thy has been doing regarding accessibility concerns with interactive tiles. The outcome will be a new experimental variant of tile visuals that will pass contrast minimums. Product teams will be allowed to test it out in product through an opt-in approach with the new variant. Below is the final task-list needed to bring the variant to stable.

Phase 1: Finalize design spec

Tasks

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1. Experimental tile: define new color tokens #12343
   role: design ✏️ +1
   
2. Experimental tile: final design spec #12279
   role: design ✏️ +1
   

Phase 2: Ready for development + production

Tasks

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1. Experimental tile: code implementation #12464
   5 of 5
   adopter: PAL role: dev 🤖 +2
   
2. Experimental tile: Update the content for tile to include experimental variant carbon-website#3261
   2 of 2
   adopter: PAL component: tile proposal: accepted role: design ✏️ type: docs 📖 type: enhancement 💡 version: 11 +7
   
3. Experimental tile: add new variant and styles to Figma carbon-design-kit#591
   adopter: PAL kit: figma role: design ✏️ type: a11y ♿ type: enhancement 💡 version: 11 +6
   
4. Experimental tile: add new variant and styles to Sketch carbon-design-kit#590
   adopter: PAL kit: sketch role: design ✏️ type: a11y ♿ type: enhancement 💡 version: 11 +6
   
5. Experimental tile: Add a new color token for the icon #13217
   component: tile role: dev 🤖 version: 11 +3
   
6. Experimental tile: Add $icon-interactive token to kit tooling #13221
   component: tile role: design ✏️ +2
   
7. Experimental tile: Add new tokens to website #13222
   component: tile role: design ✏️ +2
   
8. [Figma] add $border-tile color token carbon-design-kit#650
   kit: figma role: design ✏️ type: enhancement 💡 +3
   

Phase 3: Comms

Tasks

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1. Experimental tile: Write announcement with an explanation of the topic #12925
   component: tile role: design ✏️ type: enhancement 💡 +3
   
2. Experimental tile: Medium article highlighting the issue and proposed solutions #12926
   component: tile role: design ✏️ type: enhancement 💡 +3
   
3. Experimental tile: Post annoucement