SurfaceFlinger: add getAllowedDisplayConfigs

Add an API to ISurfaceComposer to get allowed display configurations.

Test: manual test that calls getAllowedDisplayConfigs()
Bug: 122905403
Change-Id: Ieeb04f0d002ecfb2dbb0acd22ef6f659806c3950
diff --git a/services/surfaceflinger/AllowedDisplayConfigs.h b/services/surfaceflinger/AllowedDisplayConfigs.h
index e3b9c1f..7ca62ea 100644
--- a/services/surfaceflinger/AllowedDisplayConfigs.h
+++ b/services/surfaceflinger/AllowedDisplayConfigs.h
@@ -54,6 +54,12 @@
         return (std::find(mConfigs.begin(), mConfigs.end(), config) != mConfigs.end());
     }
 
+    void getAllowedConfigs(std::vector<int32_t>* outConfigs) const {
+        if (outConfigs) {
+            *outConfigs = mConfigs;
+        }
+    }
+
 private:
     // add a config to the allowed config set
     void addConfig(int32_t config) { mConfigs.push_back(config); }