AAPT2: Ensure style strings are always first in StringPool

Move the styled strings to a separate section of the StringPool so
that sorting can never mess up the order of Styles.

Bug: 63570514
Test: make aapt2_tests
Change-Id: Id2ce1355b92be1bb31ce0daa7e54ae9b5b6c2ffe
diff --git a/tools/aapt2/ResourceValues.cpp b/tools/aapt2/ResourceValues.cpp
index 947e091..eb59175 100644
--- a/tools/aapt2/ResourceValues.cpp
+++ b/tools/aapt2/ResourceValues.cpp
@@ -253,10 +253,9 @@
 }
 
 void StyledString::Print(std::ostream* out) const {
-  *out << "(styled string) \"" << *value->str << "\"";
+  *out << "(styled string) \"" << value->value << "\"";
   for (const StringPool::Span& span : value->spans) {
-    *out << " " << *span.name << ":" << span.first_char << ","
-         << span.last_char;
+    *out << " " << *span.name << ":" << span.first_char << "," << span.last_char;
   }
 }