SF: Set up librenderengine_mocks

Move the existing mocks out of the unit test directory into
RenderEngine/include/renderengine/mock and RenderEngine/mock.

This allows other unit tests to easily reuse the mocks.

Change the unit test to use the new library and reference the moved
headers.

Test: atest libsurfaceflinger_unittest libcompositionengine_test
Bug: 121291683
Change-Id: I1577995e6140cb3949207c5bc746c46b7828ae19
diff --git a/libs/renderengine/Android.bp b/libs/renderengine/Android.bp
index d872f02..cf88a3a 100644
--- a/libs/renderengine/Android.bp
+++ b/libs/renderengine/Android.bp
@@ -79,3 +79,19 @@
         thin: true,
     },
 }
+
+cc_library_static {
+    name: "librenderengine_mocks",
+    defaults: ["librenderengine_defaults"],
+    srcs: [
+        "mock/Framebuffer.cpp",
+        "mock/Image.cpp",
+        "mock/RenderEngine.cpp",
+    ],
+    static_libs: [
+        "libgtest",
+        "libgmock",
+    ],
+    local_include_dirs: ["include"],
+    export_include_dirs: ["include"],
+}