LPS-33860 Structures and templates referenced by web contents can be removed

It's enough to check if the template is referenced by any web contents, because of the already existing constraints:

1) An structure referenced by any templates cannot be removed.
2) A web content with an structure must also have a template.
LPS-33860 Test
LPS-33860 Format source
LPS-33860 Use backend name
LPS-33860 SF
LPS-33741 Test Upgrade Uninstanceable PortletId
LPS-33741 Use a try finally, in case we add more tests in the future and the second one breaks.
LPS-33429 Fix compile error