Adds an init host lib for use in host_apex_verifier.

Includes extracting the APEX-specific SDK version naming scheme filter
logic so it can be reused when host_apex_verifier looks at rc files
inside the APEX.

Bug: 222121216
Test: Use in host_apex_verifier
Change-Id: I0396a455f30d2de71525ccd3fa69c75576054048
diff --git a/init/parser.h b/init/parser.h
index 95b0cd7..2f4108f 100644
--- a/init/parser.h
+++ b/init/parser.h
@@ -76,6 +76,12 @@
     void AddSectionParser(const std::string& name, std::unique_ptr<SectionParser> parser);
     void AddSingleLineParser(const std::string& prefix, LineCallback callback);
 
+    // Compare all files */path.#rc and */path.rc with the same path prefix.
+    // Keep the one with the highest # that doesn't exceed the system's SDK.
+    // (.rc == .0rc for ranking purposes)
+    std::vector<std::string> FilterVersionedConfigs(const std::vector<std::string>& configs,
+                                                    int active_sdk);
+
     // Host init verifier check file permissions.
     bool ParseConfigFileInsecure(const std::string& path);