[HLO Componentization] Populate hlo/testlib sub-component (Phase II).

This CL takes care of
1. Migrating external projects dependencies from

```
tensorflow/compiler/xla:test
tensorflow/compiler/xla:test_helpers
tensorflow/compiler/xla/service:pattern_matcher_gmock
```

to `tensorflow/compiler/xla/hlo/testlib:*`

PiperOrigin-RevId: 714103797

xla/python/ifrt/BUILD

@@ -410,8 +410,8 @@ cc_library(
     deps = [
         ":attribute_map",
         ":ifrt",
-        "//xla:test",
         "//xla/hlo/ir:hlo",
+        "//xla/hlo/testlib:test",
         "//xla/pjrt:pjrt_executable",
         "//xla/pjrt:pjrt_layout",
         "//xla/tsl/concurrency:ref_count",

xla/python/ifrt/mock.h

@@ -30,6 +30,7 @@ limitations under the License.
 #include "absl/types/span.h"
 #include "llvm/Support/ExtensibleRTTI.h"
 #include "xla/hlo/ir/hlo_module.h"
+#include "xla/hlo/testlib/test.h"
 #include "xla/pjrt/pjrt_executable.h"
 #include "xla/pjrt/pjrt_layout.h"
 #include "xla/python/ifrt/array.h"
@@ -52,7 +53,6 @@ limitations under the License.
 #include "xla/python/ifrt/topology.h"
 #include "xla/python/ifrt/tuple.h"
 #include "xla/python/ifrt/value.h"
-#include "xla/test.h"
 #include "xla/tsl/concurrency/ref_count.h"
 
 namespace xla {