Bugfix release for V151

Adjustments

• Fixed new tab page alignment when nova design is enabled
• Fixed panel bg color
• Fixed tab bar horizontal padding
• Fixed urlbar go button
• Fixed app panel margins
• Fixed navbar height with vertical tabs enabled
• Fixed persistent navbar border when rounded corners are enabled
• Fixed disabled menuitems using the wrong color
• Fixed split-view splitter bg color - WIP feature
• Fixed some misalignments when using vertical tabs
• Sped up staggered urlbar dropdown anims tweak