[FIX] mrp: views improvement

This commit makes some changes in the production order views
as well as in the workorders one. This commits make sure there
is now only one form view left for the mrp.workorder model.

This commit take part of the MRP refactoring
(69c48add)

Task : 2278147

X-original-commit: 8b389ab3601cf5ed9328b7ce55ee91d54aa70150