SF: Move HWComposerBufferCache in to CompositionEngine

This simply moves DisplayHardware/HWComposerBufferCache.* to
CompositionEngine/HwcBufferCache.*, adjusting the existing code to
reference the moved file and namespace.

This is a prelude to moving the layerBE state into CompositionEngine.

Test: atest libsurfaceflinger_unittest libcompositionengine_test
Bug: 121291683
Change-Id: Id1e907963d0453ec7beea285ab384a963c356f89
diff --git a/services/surfaceflinger/CompositionEngine/Android.bp b/services/surfaceflinger/CompositionEngine/Android.bp
index 1651cc4..ce6b06c 100644
--- a/services/surfaceflinger/CompositionEngine/Android.bp
+++ b/services/surfaceflinger/CompositionEngine/Android.bp
@@ -41,6 +41,7 @@
         "src/DisplayColorProfile.cpp",
         "src/DisplaySurface.cpp",
         "src/DumpHelpers.cpp",
+        "src/HwcBufferCache.cpp",
         "src/Layer.cpp",
         "src/Output.cpp",
         "src/OutputCompositionState.cpp",
@@ -82,6 +83,7 @@
         "tests/CompositionEngineTest.cpp",
         "tests/DisplayColorProfileTest.cpp",
         "tests/DisplayTest.cpp",
+        "tests/HwcBufferCacheTest.cpp",
         "tests/LayerTest.cpp",
         "tests/MockHWComposer.cpp",
         "tests/OutputTest.cpp",