Rework UI of configure widget screens

[TimoPtr]

Description

Most of our widget can be configured, but today the UI is raw and would benefits from a redesign and fit more into the application by using the same theme and colors.

Additional context

Migrate to compose and material3 and use the new entity picker #6253

[himu-gupta]

Hi! I’d like to help with this widget configuration UI migration, but I want to avoid overlapping with existing work. I see open PRs for TemplateWidgetConfigureActivity (#6444), CameraWidgetConfigureActivity (#6499), EntityWidgetConfigureActivity (#7007), and MediaPlayerControlsWidgetConfigureActivity (#7018), and ButtonWidgetConfigureActivity (#6305) looked claimed in the issue thread.

Is there a remaining widget configuration screen you’d prefer a contributor to take next for a small, scoped Compose + Material 3 PR? I’m happy to follow the patterns from the active PRs and keep the first change focused on one screen.