Previously, the import/export icons were not correctly tinted when the Android OS was set to dark mode. To correct this, the icons no longer use a hard-coded fill colour and an iconTint property is applied in order to leverage the built-in support that Chromium has for automatically adjusting icons for light/dark mode. The icons have also been replaced with the upload/download SVG paths from the brave/leo repo. Resolves brave/brave-browser#50232