[IMP] base, web: support `x_active` for archiving

While x_name has long been automatically supported as an equivalent
of name, x_active was not.

This commit adds this behaviour OoB, both in the ORM and the web client.

On the ORM-side, a new `_active_name` attribute is supported on models.
This attribute specifies the field that should behave as an active marker
for records of the model. It is supported the same way `active` has been
until now (filtering by the `active_test` context key and toggled by the
`action_archive`, `action_unarchive` and `toggle_active` methods).
Although no check has been added on the field's type, it is assumed to
be a boolean field (the same way no check is present on the `(x_)name`
field).

On the client-side, the list view and form view now both support
detecting the presence of either `active` or `x_active` on records,
automatically adding an '(Un)Archive' button in the Action menu if such
a field is detected.

Note that the ORM implementation does actually need the field to be named
in any specific way, but since the web client has no mechanism to load
information regarding a model (the lifecycle of an action loading
includes loading the action, view and record(s) but no generic
information about the model itself besides what is included in the
views), we restrict the field's name to `(x_)active` to avoid confusion
as any other name would work at the ORM-level but not in the client.

In the future, the client might be able to more elegantly get
information about models, but this was not the scope of this change and
this solution should cover most cases.

Note that the `active` field will always takes precedence over the
`x_active` field to avoid confusing the polarity, even if both fields
are present on the model.

In the case of a custom field, it might be slightly annoying that the
default value of a Boolean field is `False`, which means that upon
adding the column, all existing records are automatically archived. This
can easily be worked around using an `ir.default` record for that
particular field and an update of existing records (e.g. through the
list view). The goal of this change was not to make it easy to add
support for custom active fields, but to make it possible - we have
therefore kept this implementation which introduces few changes while
adding enough flexibility for developers.
See https://twitter.com/zubair_shafiq/status/1202587553871880192?s=20


for more info regarding supporting any `_active_name` in the web client.

Co-authored-by: Raphael Collet <rco@odoo.com>