migrate runtime/test (with PACKAGE gating) (#21433)

Summary:
Pull Request resolved: #21433

The dir's PACKAGE file uses ci.buckconfig("executorch.event_tracer_enabled")
which is not on xplat's buckconfig allowlist. Wrapped the ci.package call
in `is_fbcode() else None` so xplat skips it (the dir is fbcode-only
anyway since it was TARGETS-only pre-migration).

Then applied the standard chunk-6 transform: created targets.bzl with
define_common_targets(is_fbcode = False) early-returning outside fbcode,
replaced TARGETS with thin BUCK.

Reviewed By: ndmitchell

Differential Revision: D109081975

Author: bigfootjon

runtime/test/BUCK

@@ -0,0 +1,9 @@
+# Any targets that should be shared between fbcode and xplat must be defined in
+# targets.bzl.
+
+load("@fbsource//tools/build_defs:fbsource_utils.bzl", "is_fbcode")
+load(":targets.bzl", "define_common_targets")
+
+oncall("executorch")
+
+define_common_targets(is_fbcode = is_fbcode())

runtime/test/TARGETS

@@ -0,0 +1,36 @@
+load("@fbsource//xplat/executorch/build:runtime_wrapper.bzl", "runtime")
+
+def define_common_targets(is_fbcode = False):
+    if not is_fbcode:
+        return
+
+    runtime.python_test(
+        name = "test_runtime",
+        srcs = ["test_runtime.py"],
+        deps = [
+            "//executorch/extension/pybindings/test:make_test",
+            "//executorch/runtime:runtime",
+            "//executorch/devtools/etdump:serialize",
+        ],
+    )
+
+    runtime.python_test(
+        name = "test_runtime_etdump_gen",
+        srcs = ["test_runtime_etdump_gen.py"],
+        deps = [
+            "//executorch/extension/pybindings/test:make_test",
+            "//executorch/runtime:runtime",
+            "//executorch/devtools/etdump:serialize",
+        ],
+    )
+
+    runtime.python_test(
+        name = "test_runtime_xnnpack",
+        srcs = ["test_runtime_xnnpack.py"],
+        deps = [
+            "//caffe2:torch",
+            "//executorch/backends/xnnpack/partition:xnnpack_partitioner",
+            "//executorch/exir:lib",
+            "//executorch/runtime:runtime",
+        ],
+    )