Revert "evas: Add source_region property to proxy objects"

Revert "evas: Add source_region property to proxy objects"

This reverts commit 4e110a34bffe09abe4dd793f9ecf1cf3884ccf22.

Urgh. I'm stupid. Conceptually I still like the idea of the
region proxy, that only renders part of the source object
in a proxy surface. The problem right now is that the proxy
subrender mechanism renders to a surface that belongs to
the **source** and not the proxy object. As a consequence,
the region would become a property of the source, rather than
the proxy, which is not at all the intention of the original
patch. In other words, everything would fall apart if an object
has more than one proxy, for whatever reason.

I realized that when trying to actually test the region proxy.
It didn't work at all. Revert for now.