GLSP-Playwright Tests for already existing features

[haydar-metin]

This issue provides an overview of the E2E tests for the already existing features and their state (e.g., WIP). Please do not add new features here, create a separate issue in the future. This issue only serves as an overview to know the progress.

Feature	PR	State
Model Saving
Model Dirty State
Model SVG Export
Model Layout
Restoring viewport on re-open
Model Edit Modes - Edit - Read-only
Client View Port - Center - Fit to Screen
Client Status Notification
Client Message Notification
Client Progress Reporting
Element Selection	eclipse-glsp/glsp-playwright#7	Finished
Element Hover	eclipse-glsp/glsp-playwright#9
Element Validation		WIP - @haydar-metin
Element Navigation
Element Type Hints
Element Creation and Deletion
Node Change Bounds - Move - Resize
Node Change Container
Edge Reconnect
Edge Routing Points
Ghost Elements
Element Text Editing
Clipboard (Cut, Copy, Paste)
Undo / Redo
Contexts - Context Menu - Command Palette - Tool Palette
Accessibility Features (experimental) - Search - Move - Zoom - Resize
Helper Lines (experimental)

Reference: #1154