[IMP] web calendar: Keep width box while drag or resize

When there are many events at the same moment in a calendar,
events are thin and on mouse hover the event take all the width.

Before this commit, when we drag or we resize a event in calendar,
the event returns to the state thin.

After this commit, the width event stay width during resizing and
draging.

closes odoo/odoo#37334

Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>