[IMP] web: remove readonly mode of form view

This commit does multiple things:
- The readonly mode of form view is removed but not for the fields.
  it means that the fields in the view are always in edit mode except
  if we force them to be readonly.
- The control panel is revamped to take less vertical space and shows now
  the record editing (dirtiness)/validity status after editing the record.
- The record is saved only when leaving the view or by clicking the save
  button when hovering the record status in the control panel.
- The record can still be discarded by clicking the discard button when
  hovering the status text in control panel.

task id: 2822553

Part-of: odoo/odoo#100570
Co-authored-by: luvi <luvi@odoo.com>