Aggregating prior discussions from abandoned PRs.

• Update PanelPart with ViewContainer logic existing in ActivityBarPart with support for hiding a panel when empty Port view container logic from activitybarpart to panelpart #87444
• Abstract viewlet/panel creation away Register viewlet or panel when view container is registered #87246
• Use views service to move views between containers Enhance view service to support moving views #87461
• Support tracking view position on reload Add cache to viewdescriptorservice #88656
• Add generic move to panel / move to sidebar commands for movable views Add movable property to views and add toggle view commands #88823
• Fix issue with render being called twice for header actions. Fix Header Actions double rendering #88433
• Add movable property to views and enforce icon per view Add movable property to views and add toggle view commands #88823
• Update theming for views to support panel theming
• Move search view to new model migrate search to use new setting #89190
• Enable outline view to move Enabled movable Custom Views #89240
• Enable custom views to move Enabled movable Custom Views #89240
• Provide method for views to persist state during move
• Introduce ability to contribute a View to a Panel for extensions (should have its own item)