Use segment length to make dropdown responsive

[nathangavin]

Above 600px, the dropdown has a min width of 240px, and a max width of 320px. The width of the dropdown will grow to match the longest segment name.

Below 600px, the width of the dropdown is fixed to the same size as the parent button.

fixes #21291

Review

• Functional review done
• Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• Security review done
• Wording review done
• Code review done
• Tests were added if useful/possible
• Reviewed for breaking changes
• Developer changelog updated if needed
• Documentation added if needed
• Existing documentation updated if needed