Multiuser review, login/register refactor and welcome screen

• Account switcher transition up/down
• Account switcher match designs
• Refactor login/register modals
• Remove old login components and screens
• Add welcome screen (Mani)
• Fix support for the reset password flow (Welcome screen should handle the deep link)
• Fix the transparent layer of the welcome screen to match the designs
• Remove fixed dark color into ResetPassword modal
• Fix double border in grouped Menu Item components
• Fix spec tests

closes #3600 (closed) #3605 (closed)