[FIX] account: prevent recomputation of related field `internal_type`
[FIX] account: prevent recomputation of related field `internal_type`

When creating a new `account.account`,
or writing on an existing one, changing the
`type`, the source of the related field
`internal_type`, `user_type_id.type`, was
re-written (re-stored) because the field
was not read-only.

In addition, the re-store of the value
of this field triggered the re-store of the related
field `internal_type` on all other `account.account`
records using this `internal_type`, which leaded to:
 - Performance issues
 - Potential access rights issues, if this leaded
   to write operations on records to which the user
   does not have the access (multi-company rules, among others)

Forcing the field as read-only allow to not pass the value of this
`internal_type` from the web client to the server when
creating or editing an `account.account`.

Besides, the field is required in the view, to correctly trigger
the according onchange method:
```
@api.onchange('internal_type')
def onchange_internal_type(self):
```

opw-660292
Closes #10143

bplancher/odoo,Elico-Corp/odoo_OCB,ygol/odoo,ygol/odoo,hip-odoo/odoo,storm-computers/odoo,stephen144/odoo,ygol/odoo,microcom/odoo,stephen144/odoo,bplancher/odoo,dfang/odoo,laslabs/odoo,bplancher/odoo,dfang/odoo,microcom/odoo,hip-odoo/odoo,Elico-Corp/odoo_OCB,ygol/odoo,laslabs/odoo,storm-computers/odoo,dfang/odoo,Elico-Corp/odoo_OCB,sysadminmatmoz/OCB,microcom/odoo,dfang/odoo,laslabs/odoo,sysadminmatmoz/OCB,sysadminmatmoz/OCB,sysadminmatmoz/OCB,storm-computers/odoo,ygol/odoo,Elico-Corp/odoo_OCB,sysadminmatmoz/OCB,laslabs/odoo,stephen144/odoo,sysadminmatmoz/OCB,microcom/odoo,hip-odoo/odoo,ygol/odoo,ygol/odoo,bplancher/odoo,stephen144/odoo,sysadminmatmoz/OCB,dfang/odoo,hip-odoo/odoo,stephen144/odoo,laslabs/odoo,storm-computers/odoo,dfang/odoo,storm-computers/odoo,microcom/odoo,Elico-Corp/odoo_OCB,laslabs/odoo,bplancher/odoo,storm-computers/odoo,Elico-Corp/odoo_OCB,hip-odoo/odoo,microcom/odoo,stephen144/odoo,hip-odoo/odoo,bplancher/odoo