Fixes for docs and DashboardLayout component

[apedroferreira]

• Prevents autocomplete issue with search bar demo in DashboardLayout docs (Closes https://github.com/mui/mui-toolpad/issues/4037)
• Fixes misaligned search icon in mobile view of search/slots demo in DashboardLayout docs
• Fixes header left spacing in desktop view when using disableCollapsibleSidebar prop
• Fixes components not using demo iframe window width when using useMediaQuery hook
• Fixes segments in DashboardLayout navigation item actions demo (there were extra slashes)

https://deploy-preview-4104--mui-toolpad-docs.netlify.app/toolpad/core/react-dashboard-layout/

Before: https://mui.com/toolpad/core/react-dashboard-layout/