[lldb-vscode] Use SBFrame.GetDisplayFunctionName() instead of SBFrame.GetFunctionName()

[ivanhernandez13]

Summary

This change replaces calls to SBFrame.GetFunctionName() with
SBFrame.GetDisplayFunctionName() which can return much more user
friendly names in some cases, particularly for Swift code.

A trivial example:

main.swift

class Doer {
    static func doTheThing() {
        print("Hello World!")
    }
}
Doer.doTheThing()

lldb

(lldb) script
>>> frame = lldb.debugger.GetSelectedTarget().GetProcess().GetSelectedThread().GetSelectedFrame()
>>> frame.GetDisplayFunctionName()
'static Doer.doTheThing()'
>>> frame.GetFunctionName()
'static main.Doer.doTheThing() -> ()'

lldb/tools/lldb-vscode/JSONUtils.cpp

if (symbol.IsValid()) {
         disasm_line = g_vsc.GetLineForPC(addr_srcref->second, pc);
       } else {
         insts = symbol.GetInstructions(g_vsc.target);
       }
     }
   }
   const auto num_insts = insts.GetSize();
   if (low_pc != LLDB_INVALID_ADDRESS && num_insts > 0) {
-    EmplaceSafeString(object, "name", frame.GetFunctionName());
+    EmplaceSafeString(object, "name", frame.GetDisplayFunctionName());
     SourceReference source;
     llvm::raw_string_ostream src_strm(source.content);
     std::string line;
     for (size_t i = 0; i < num_insts; ++i) {
       lldb::SBInstruction inst = insts.GetInstructionAtIndex(i);
       const auto inst_addr = inst.GetAddress().GetLoadAddress(g_vsc.target);
       const char *m = inst.GetMnemonic(g_vsc.target);
       const char *o = inst.GetOperands(g_vsc.target);

 //   "required": [ "id", "name", "line", "column" ]
 // }
 llvm::json::Value CreateStackFrame(lldb::SBFrame &frame) {
   llvm::json::Object object;
   int64_t frame_id = MakeVSCodeFrameID(frame);
   object.try_emplace("id", frame_id);
 
   std::string frame_name;
-  const char *func_name = frame.GetFunctionName();
+  const char *func_name = frame.GetDisplayFunctionName();
   if (func_name)
     frame_name = func_name;
   else
     frame_name = "<unknown>";
   bool is_optimized = frame.GetFunction().GetIsOptimized();
   if (is_optimized)
     frame_name += " [opt]";
   EmplaceSafeString(object, "name", frame_name);