Improve visual appearance of form elements outline

[marcelbertram]

Scope

Evaluate improvements and efforts for making default border for forms more decent (lighter grey) so that form elements are not that "boxy" in design and to improve the visual differentiation of the focus state.

Notes

• Pair with Dev on actual implementation (possibilities)
• Align with segmented control? https://designsystem.porsche.com/latest/components/segmented-control/examples
• Bug report focus state: https://github.com/porsche-design-system/porsche-design-system/issues/2702

Acceptance Criteria

• [ ] Decision on refinement of outline color for form elements done
• [ ] If required changes done in Figma library as spec for dev change