[Form] Pin clear selection above sorted visit options

[Montekkundan]

Brief summary of changes

• Adds an optional pinnedOption property to SelectElement when option sorting is enabled.
• Adds the property to the SelectElement TypeScript declaration.
• Pins the Clear Selection option above the sorted dashboard visit options.
• Uses the stable __clear__ option key so translated labels do not affect the pinned option.
• Keeps the remaining visit options alphabetically sorted.

Testing instructions

• Configure a visit with a label beginning with a special character, such as (Screening).
• Run target=statistics npm run compile.
• Open http://localhost:8080/.
• Open the filters for a dashboard chart.
• Confirm -- Clear Selection -- appears above the special-character visit.
• Confirm the remaining visits remain alphabetically sorted.
• Select the special-character visit and confirm it can be cleared using -- Clear Selection --.

Link(s) to related issue(s)

• Resolves [Form] SelectElement Pin Option To Top #10987