[IMP] website: properly show navbar on iPad

Currently, when we open the website on iPad, the navbar is not displayed
properly (systray items are overlapping on the website menu). This
commit fixes the issue by using '+' icon on the navbar top menus if
there is not ample space. This commit also converts multi company
selector with 'fa-building' and multi website selector with 'fa-globe'
icons on smaller screens.

task-1945020

closes odoo/odoo#32321

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>