[vmtest] Allow passing labels to vmtest target

Summary: Currently we can only pass labels to the wrapper but not the vmtest target itself. Add vm_test_labels field so that we can modify CI behaviors of the vmtest.

Test Plan: CI

Reviewed By: elibus

Differential Revision: D89127808

fbshipit-source-id: c1910d712ee5a5727b537e8c6c408f9da84d76e4

Author: lnyng

antlir/antlir2/antlir2_vm/bzl/test.bzl

@@ -238,6 +238,7 @@ def _implicit_vm_test(
         expect_failure: bool = False,
         postmortem: bool = False,
         labels: list[str] | None = None,
+        # @oss-disable
         output_dirs: list[str] | None = None,
         systemd_credentials: dict[str, str] | None = None,
         _add_outer_labels: list[str] = [],
@@ -274,6 +275,7 @@ def _implicit_vm_test(
     # @oss-disable
     labels = ["uses_sudo"]
     # @oss-disable
+    # @oss-disable
 
     inner_test_name = name + "_vm_test_inner"
     test_rule(