[FIX] web: highlight clickable pivot cells on hover

After a recent reorganization of the web client's components tree, the
class 'o_enable_linking' was added on the wrong element. This made the
css rule responsible of the highlighting of the clickable pivot cells
impossible to satisfy.

This commit fixes the issue by adding the class directly in the template
'PivotView'.

Additionally, this commit also makes visually clear when a field
selection menu-items is disabled (because it is already used) using
a 'not-allowed' cursor (which was removed in bs4). It is now again
possible to open a list view by clicking on a cell with zero value
(like in Odoo 11).

task-1916889

closes odoo/odoo#34165

Signed-off-by: VincentSchippefilt <VincentSchippefilt@users.noreply.github.com>