[FIX] web: action service: concurrency issue

There is a concurrency issue in the action service:
 1) be in an action with several views
 2) execute another action (e.g. by clicking on a menu)
  -> [calls the route "/web/action/load", and it takes a while]
 3) meanwhile, click on another view in the view switcher

If the call to "/web/action/load" is long enough, it may happen
that the view requested in step 3 is briefly shown before the
action associated with the menu clicked in step 2.

In this scenario, the action of step 2 should never be displayed,
because the user requested something else afterwards (in this
case a switch view).

One can produce a similar issue when restoring a previous action
of the breadcrumbs instead of switching view.

This commit fixes those two issues by registering a resolved
promise in the keepLast (concurrency utils), s.t. it "cancels"
the potential current operation (in this case, the call to
"/web/load/action").

closes odoo/odoo#87127

Signed-off-by: Mathieu Duckerts-Antoine <dam@odoo.com>