Texture opened from editor UX/UI changes

[jiajasper]

When a texture image is opened from the editor:

1. We collapsed the left panel and let the texture viewport takes more screen real estate since the image opened from the editor are not displayed in the file hierarchy panel
2. We add a "go back" button on the tab for users to go back to the editor from texture tool - it will open the texture inspector panel automatically when the user is back in the editor

Figma link: https://www.figma.com/file/tgjz0PLgrPoJ9gh6nqkNGw/PlayCanvas-Texture-Viewer?node-id=14%3A535