Update GovBanner Component

[sreidthomas]

GovBanner needed some updates to improve styles and behavior

• The down chevron should rotate 180 degrees when the dropdown opens/closes to indicate the link now closes/opens the dropdown
• The display of the content container should use an ease-in-out animation instead of abruptly appearing
• The info section should be have a part attribute enabling it to be styled from the light DOM. Specifically, I should be able to override the left and right margins of the content so that the edges line up with the main content of the site where the banner is used.

[jedgar1mx]

The child element should not have the aria-expanded attribute

[maxatdetroit]

Just a couple small tweaks requested. Nice work.

[maxatdetroit]

I'm not sure what changed but the animation is now very jerky and the background color of the content area is incorrect on the left/right. Would you please correct those things?

Screen.Recording.2025-05-06.101537.mp4

[sreidthomas]

2025-05-22.13-43-55.mp4

[maxatdetroit]

@sreidthomas could you merge in dev and resolve the conflicts? Sorry for the conflicts. I had to make some nontrivial changes in #350 to support a feature for the site launch this week.