[string] Move String.p.toLowerCase to CSA

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index d0409fd8e2e040396b66e5ef23518fb7b332ead4..5a41658711a6b9b9a80eff1083c924d267c3166d 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -919,6 +919,7 @@ v8_source_set("v8_builtins_generators") {
     "src/builtins/builtins-ic-gen.cc",
     "src/builtins/builtins-internal-gen.cc",
     "src/builtins/builtins-interpreter-gen.cc",
+    "src/builtins/builtins-intl-gen.cc",
     "src/builtins/builtins-math-gen.cc",
     "src/builtins/builtins-number-gen.cc",
     "src/builtins/builtins-object-gen.cc",
@@ -996,6 +997,10 @@ v8_source_set("v8_builtins_generators") {
     ]
   }
 
+  if (!v8_enable_i18n_support) {
+    sources -= [ "src/builtins/builtins-intl-gen.cc" ]
+  }
+
   configs = [ ":internal_config" ]
 }