Add feature flag, and support for new secure settings in framework

The secure setting is only updated and guarded with feature flag.
Reason for single update rather than 2 separate API to update level vs
mode : In Daltonizer.cpp either of the change requires re-calculation of
all matrices (current implementation). We can optimize further later
once we have basic functionality implemented and working.

Test: Locally tested
Bug: 322829049
Flag: com.android.server.accessibility.enable_color_correction_saturation

Change-Id: Ic919c7f01ce4723ecf933b7bdc25a530e372f5ae
diff --git a/services/accessibility/accessibility.aconfig b/services/accessibility/accessibility.aconfig
index 82579d8..2b18b7d 100644
--- a/services/accessibility/accessibility.aconfig
+++ b/services/accessibility/accessibility.aconfig
@@ -183,3 +183,10 @@
         purpose: PURPOSE_BUGFIX
     }
 }
+
+flag {
+    name: "enable_color_correction_saturation"
+    namespace: "accessibility"
+    description: "Feature allows users to change color correction saturation for daltonizer."
+    bug: "322829049"
+}
\ No newline at end of file