Create new viewport component to replace DaffSidebarViewport

[damienwebdev]

PR Checklist

• Commit message follows our contributing guidelines
• Tests added/updated (for bug fixes/features)
• Documentation added/updated (for bug fixes/features)

PR Type

• Bug fix
• Feature
• Style update
• Refactor
• Test
• Build
• CI
• Docs
• Performance
• Other (please describe)

Current behavior

Currently, the DaffSidebarViewportComponent uses @angular/animations and doesn't use signals. It's also rather clunky to use because it doesnt internally handle state which means you have to wire everything up yourself.

Fixes: #3528

New behavior

DaffViewportComponent uses signals, no Angular animations and can manage state internally by default.

Breaking change?

• Yes
• No

Additional context

[xelaint]

TO DO:

• Outline what is in the public api.
• Make sure stateless true / false works.

DIFFS:

• Create new viewport
• Deprecate sidebar-viewport
• Remove extraneous header component from app / registrations
• Replace sidebar viewport with viewport in all examples
• Replace sidebar viewport with viewport in daffio