LPS-33741 Make Image Gallery Instanceable

Hi Julio,

For the upgrade process I based the logic on the existing UpgradePortletId class. Some remarks:

* We use the same instanceId for all pages, asuming that since portlets were initially non-instanceable, the pair plid-portletId will remain unique. This makes the upgrade process much simplier.
* No changes in Portlet and ResourceAction tables (i.e. no call to updatePortlet)
* For ResourcePermission, only the primaryKey is upgraded (but not the name).

I do not consider it necessary to create a test for this feature, since most of the logic comes from UpgradePortletId and it already has a test class. However, if you think we need it, I can create a new test.

Thanks