tests: enable trusted ephemeral storage for runtime-rs

Remove the runtime-rs skip from the trusted ephemeral data storage
test now that runtime-rs implements block-encrypted emptyDir volumes.

Also remove the genpolicy drop-in that disabled encrypted_emptydir
for runtime-rs and the corresponding copy logic in tests_common.sh.

Signed-off-by: Fabiano Fidêncio <ffidencio@nvidia.com>
Assisted-by: Cursor <cursoragent@cursor.com>

src/tools/genpolicy/drop-in-examples/20-runtime-rs-drop-in.json

@@ -1,7 +0,0 @@
-[
-  {
-    "op": "replace",
-    "path": "/cluster_config/encrypted_emptydir",
-    "value": false
-  }
-]