[FIX] mrp(workorder_hr): fix workorder times

Fix workorder times problems:
- sum in workorders list view
  (displays numeric value rather than mins:secs)
- timers sometimes starts at -00:01
- almost all tablet view actions reset the timer (click burger, ...)
- clicking pause stops the timer at the next second
- seconds are lost in employee timers

Task: 2985735
Part-of: odoo/odoo#105410