gpu: [compute] unify resource cleanup

Rename all resource release methods to "Release", and release all
resources with a slice and loop.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/gpu.go

@@ -398,7 +398,7 @@ func (g *gpu) Release() {
 	g.drawOps.pathCache.release()
 	g.cache.release()
 	if g.timers != nil {
-		g.timers.release()
+		g.timers.Release()
 	}
 	g.ctx.Release()
 }