[FIX] base, website: replicate inherit_id update on cow view

Before this commit, only whitelisted fields would be updated on cow views
during a module update.
A field would be whitelisted if he had the same value than the original view,
see it as a heuristic to not write on modified fields.

But `inherit_id` is not that simple, even if the cow view has a different value
than its original view, it doesn't mean it was modified by the user, it is just
because of the cow mechanism that assigned a copied view as inherit_id, which
is just a copy ofthe original one.

We can thus consider `inherit_id` as unchanged and whitelist it if the `key` is
the same.

In practice, it means that cow'd views did not receive the `inherit_id` updates
as in commit https://github.com/odoo/odoo/commit/c8577568a1e39f6692889b3e21652fa3b8df06b2#diff-823e5db841dca1798ff1300e243059a4e1c93343598d2be5a1d1dcd1d2d0c273R537
where `portal.my_account_link` had its `inherit_id` changed from
`portal.frontend_layout` to `portal.user_dropdow`, see https://github.com/odoo/upgrade/pull/2059:

Considering a module update changing `inherit_id` of D from A to B, the
following use cases are expected. Without this fix, D' never move:

CASE 1
  A    A'   B                      A    A'   B
  |    |                 =>                 / \
  D    D'                                  D   D'

CASE 2
  A    A'   B    B'               A    A'   B   B'
  |    |                 =>                 |   |
  D    D'                                   D   D'

CASE 3
    A    B                        A    B
   / \                   =>           / \
  D   D'                             D   D'

CASE 4
    A    B    B'                  A    B   B'
   / \                   =>            |   |
  D   D'                               D   D'

Opw: 2422773
Opw: 2422727
Opw: 2422770
Opw: 2423406
Opw: 2423859

X-original-commit: 2951ed681aa5e31563e501de691716806ddb46bd