[Tile] Naming convention and clearer usage of accessible vs inaccessible tiles

[laurenmrice]

• Make the experimental guidance of tile to be more clear. This is Anna's feedback:

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Usage tab

1. Inline info notification: Update the name "experimental tile" to something more descriptive.

Storybook calls it "improved contrast tile", not sure if that's the perfect name but would align. The static/read only tile actually did not change, but there is improved contrast to better cue the interactive tile. It's the distinction that's become more accessible. Maybe add a paragraph explaining this. "improved contrast (interactive) tile"

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2. Old tile versus new tile style: Explain better the usage of tiles with and without a border

• Users might still be confused about the old tile and the new tile style, especially if they reference the storybook.
• Make it clearer to the user why they are different and what they are/aren't supposed to use
• Think about if we should explain anywhere on the page why we have added a border.

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Possible tasks

• [ ] Decide on a proper name and state this out consistently in our guidance
• [ ] Organize content or have a section explaining about the difference between accessible and inaccessible tiles

[tay1orjones]

Something that might be helpful to frame up the experimental nature is to identify the new Tile features as opt-in via feature flags, as proposed in this PR https://github.com/carbon-design-system/carbon/pull/13382

https://deploy-preview-13382--carbon-components-react.netlify.app/?path=/story/experimental-feature-flags-enable-experimental-tile-contrast-tile--clickable

[sstrubberg]

Refinement call with me, lauren, jeannie, and thy