fix(picker): add picker attribute to nested popover and styles to constrain to picker width

[cdransf]

Description

This PR adds styles to the popover.css to enforce a fixed width when the popover is used within the picker component. This aligns with the design documentation and the picker component styles.

Motivation and context

Without this change the rendered picker options will grow in width without wrapping for longer labeld.

Related issue(s)

• fixes SWC-562

Author's checklist

• I have read the CONTRIBUTING and PULL_REQUESTS documents.
• I have reviewed at the Accessibility Practices for this feature, see: Aria Practices
• I have added automated tests to cover my changes.
• I have included a well-written changeset if my change needs to be published.
• I have included updated documentation if my change required it.

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Manual review test cases

1. Navigate to the picker docs
2. Open the picker
3. Edit one of the options in the inspector, changing the label text to something much longer than the default.
4. See that the label wraps rather than causing the dropdown to grow horizontally.

Device review

• Did it pass in Desktop?
• Did it pass in (emulated) Mobile?
• Did it pass in (emulated) iPad?

[changeset-bot]

⚠️ No Changeset found

Latest commit: ce748c7

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[github-actions]

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[github-actions]

Tachometer results

Currently, no packages are changed by this PR...

[coveralls]

Pull Request Test Coverage Report for Build 18197764400

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.003%) to 97.919%

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Totals
Change from base Build 18196292250:	0.003%
Covered Lines:	34050
Relevant Lines:	34574

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💛 - Coveralls

[castastrophe]

Would love your thoughts on my suggestion!

[rubencarvalho]

Changes look good to me, however I'm wondering if this is expected / desired?

[rubencarvalho]