Add option to provide custom styling to project_dropdown_filter

What does this MR do and why?

Describe in detail what your merge request does and why.

This is a follow-up for Dropdown Pajamas migration

Current migration broke a layout in compliance report

This MR fixes this issue and adds ability to add custom styling for a toggle element.

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The dropdown is shared by:

• Group > Security & Compliance > Compliance report
• Group > Analytics > Value stream
• Group > Analytics > Productivity

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