Use jinja2 for make_runtime_features and make_internal_runtime_flags

Source/core/scripts/templates/InternalRuntimeFlags.idl.tmpl

Index: Source/core/scripts/templates/InternalRuntimeFlags.idl.tmpl
diff --git a/Source/core/scripts/templates/InternalRuntimeFlags.idl.tmpl b/Source/core/scripts/templates/InternalRuntimeFlags.idl.tmpl
new file mode 100644
index 0000000000000000000000000000000000000000..8c1e2e50ec9def360827d69df5e5a75efc48c336
--- /dev/null
+++ b/Source/core/scripts/templates/InternalRuntimeFlags.idl.tmpl
@@ -0,0 +1,14 @@
+{{ license }}
+[
+    ImplementationLacksVTable
+] interface InternalRuntimeFlags {
+{%- for feature in features if not feature.custom %}
+{#-
+    Currently assuming that runtime flags cannot be changed after startup
+    it's possible that some can be and should be conditionally readonly.
+#}
+    {% if feature.condition -%} [Conditional={{feature.condition}}] {% endif -%}
+    readonly attribute boolean {{feature.first_lowered_name}}Enabled;
+{%- endfor %}
+};
+