Add is_inherited field for each API in generated .vts file

* Currently if a HAL interface is extended from another inteface,
  hidl-gen will generate all methods (both inherited and defined within
  the interface) in the output .vts file. Add the flag is_inherited to
  distinguish the ones inherited from other APIs.
* This is used in vts to get the total APIs defiend with each interface
  which which be used for API coverage measurment.

Bug: 110851162
Test: make vts
Change-Id: I307178d1c849b5dc8be01338b458cb96e6dc1294
diff --git a/Interface.cpp b/Interface.cpp
index e0c99d6..9fb7442 100644
--- a/Interface.cpp
+++ b/Interface.cpp
@@ -918,7 +918,7 @@
     }
 }
 
-void Interface::emitVtsMethodDeclaration(Formatter& out) const {
+void Interface::emitVtsMethodDeclaration(Formatter& out, bool isInherited) const {
     for (const auto &method : methods()) {
         if (method->isHidlReserved()) {
             continue;
@@ -927,6 +927,7 @@
         out << "api: {\n";
         out.indent();
         out << "name: \"" << method->name() << "\"\n";
+        out << "is_inherited: " << (isInherited ? "true" : "false") << "\n";
         // Generate declaration for each return value.
         for (const auto &result : method->results()) {
             out << "return_type_hidl: {\n";