ASTDumper: Do not escape Unicode chars in quoted fields

Context: #68438 (comment)

Author: AnthonyLatsis

lib/AST/ASTDumper.cpp

@@ -32,6 +32,7 @@
 #include "swift/Basic/Defer.h"
 #include "swift/Basic/QuotedString.h"
 #include "swift/Basic/STLExtras.h"
+#include "swift/Basic/StringExtras.h"
 #include "clang/AST/Type.h"
 #include "llvm/ADT/APFloat.h"
 #include "llvm/ADT/SmallString.h"
@@ -180,7 +181,7 @@ class escaping_ostream : public raw_ostream {
 
 private:
   virtual void write_impl(const char *Ptr, size_t Size) override {
-    base_os.write_escaped(StringRef(Ptr, Size), /*UseHexEscapes=*/true);
+    writeEscaped(StringRef(Ptr, Size), base_os);
   }
 
   virtual uint64_t current_pos() const override {

unittests/AST/ASTDumperTests.cpp

@@ -52,6 +52,6 @@ TEST(ASTDumper, ArchetypeType) {
   }
 
   EXPECT_EQ(str,
-            " name=\"\\xCF\\x84_0_0\"\n"
+            " name=\"τ_0_0\"\n"
             "  (interface_type=generic_type_param_type depth=0 index=0 param_kind=type))\n");
 }