cmGeneratorTarget: Avoid boolean trap in usage requirement lookup

Replace `bool usage_requirements_only` arguments with a proper
enumeration to clarify meaning at call sites.
diff --git a/Source/cmLinkItemGraphVisitor.cxx b/Source/cmLinkItemGraphVisitor.cxx
index 7ad8690..d87d183 100644
--- a/Source/cmLinkItemGraphVisitor.cxx
+++ b/Source/cmLinkItemGraphVisitor.cxx
@@ -107,8 +107,8 @@
     }
   }
 
-  const auto* interfaceLibraries =
-    target.GetLinkInterfaceLibraries(config, &target, true);
+  const auto* interfaceLibraries = target.GetLinkInterfaceLibraries(
+    config, &target, cmGeneratorTarget::LinkInterfaceFor::Usage);
   if (interfaceLibraries != nullptr) {
     for (auto const& lib : interfaceLibraries->Libraries) {
       auto const& name = lib.AsStr();