In the dashboard action, when switching from dashboard to dashboard, the
size of the control panel flickers. That's because the Share button is not
displays while the dashboard is loading and it takes some place, making
the control panel taller when it's displayed.
With this commit, the Share button is always displayed (disabled when the model
isn't loaded). In addition to fix the size flickering issue, it's also less
things appearing/disappearing from the UI (less sapin de Noël)
closesodoo/odoo#138816
Signed-off-by: Rémi Rahir (rar) <rar@odoo.com>