Improve styling of Page Builder info bar:

• Add a line at bottom in order to make it easier for users to differentiate where it info-bar ends and where content begins;
• Harmonize colors, based on color custom variables;
• Harmonize switchers icons sizes with the size defined in the other switcher views within the app;
• Harmonize icon size for Create button with the size defined for the same button in other views within the app;
• Increase the thickness (to 2px) of the dropdown caret for better usability in lower screen resolutions.