zink: avoid ballooning of copy box tracking

zink: avoid ballooning of copy box tracking

* if the proposed box is smaller than an existing box then don't add it,
* if the proposed box is adjacent to an existing box, expand
* if the proposed box is larger than an existing box, replace

this reduces the chances of having a ton of copy boxes to iterate over

also add a perf warning in case a ton of copy boxes exist

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21665>