[lldb] Do not return old Swift mangled symbols from resolvePointerAsSymbol (#3967)

`isSwiftSymbol()` returns true for old Swift type mangling, which is any symbol starting with `"_T"`. This is unwanted, so the check is expanded to exclude regular symbols that happen to collide with the old prefix.

(cherry picked from commit 652a6fd)

Author: kastiglione

lldb/source/Plugins/LanguageRuntime/Swift/LLDBMemoryReader.cpp

@@ -162,7 +162,8 @@ LLDBMemoryReader::resolvePointerAsSymbol(swift::remote::RemoteAddress address) {
     auto mangledName = symbol->GetMangled().GetMangledName().GetStringRef();
     // MemoryReader requires this to be a Swift symbol. LLDB can also be
     // aware of local symbols, so avoid returning those.
-    if (swift::Demangle::isSwiftSymbol(mangledName))
+    using namespace swift::Demangle;
+    if (isSwiftSymbol(mangledName) && !isOldFunctionTypeMangling(mangledName))
       return {{mangledName, 0}};
   }