WIP: glocalfile: Add x-gvfs-notrash cache

The g_unix_mount_get function is called each time when querying info, or enumerating dir. It seems that it causes performance issues in some cases on some platforms for certain g_unix_mount_get implementations, see !1707 (merged). The g_unix_mount_get call was introduced by the commit 4602a5ee and commit 4602a5ee, which are needed to set the access::can-trash attribute now. Let's use the already existing mount cache to improve the performance in this case.