[trace] Add instruction control flow kind to JSON trace dumper's output

[jj10306]

Summary

D128477 adds a '-k' flag which displays each instruction's control flow in the thread trace dump instructions command's non-json output (ie no '-j' or '-J' flag)
This diff adds the instruction control flow kind to the thread trace dump instructions command's JSON output (ie '-j' or '-J' flag)

Test Plan:
Confirm "controlFlowKind" is present in JSON when '-k' is provided

(lldb) thread trace dump instructions -J -k
[
  {                                                                                                                                                                                                                                                                                 [141/1952]
    "id": 7755,
    "loadAddress": "0x400868",
    "module": "test.out",
    "symbol": "main",
    "mnemonic": "jmp",
    "controlFlowKind": "jump",
    "source": "/home/jakobjohnson/jakob-dev/test.cpp",
    "line": 41,
    "column": 29
  },
  {
    "id": 7753,
    "loadAddress": "0x7ffff7b54dab",
    "module": "libstdc++.so.6",
    "symbol": "std::ostream::flush()",
    "mnemonic": "retq",
    "controlFlowKind": "return"
  },
  {
    "id": 7752,
    "loadAddress": "0x7ffff7b54daa",
    "module": "libstdc++.so.6",
    "symbol": "std::ostream::flush()",
    "mnemonic": "popq",
    "controlFlowKind": "other"
  },
  ...
]

Confirm "controlFlowKind" is not present when '-k' isn't provided

(lldb) thread trace dump instructions -J
[
  {
    "id": 7755,
    "loadAddress": "0x400868",
    "module": "test.out",
    "symbol": "main",
    "mnemonic": "jmp",
    "source": "/home/jakobjohnson/jakob-dev/test.cpp",
    "line": 41,
    "column": 29
  },
  {
    "id": 7753,
    "loadAddress": "0x7ffff7b54dab",
    "module": "libstdc++.so.6",
    "symbol": "std::ostream::flush()",
    "mnemonic": "retq"
  },
  {
    "id": 7752,
    "loadAddress": "0x7ffff7b54daa",
    "module": "libstdc++.so.6",
    "symbol": "std::ostream::flush()",
    "mnemonic": "popq"
  },

[persona0220]

lgtm!

lldb/source/Target/TraceDumper.cpp

| {
       "hwClock"?: string decimal,
       "timestamp_ns"?: string decimal,
       "module"?: string,
       "symbol"?: string,
       "line"?: decimal,
       "column"?: decimal,
       "source"?: string,
       "mnemonic"?: string,
+      "controlFlowKind"?: string,
     }
   */
 public:
   OutputWriterJSON(Stream &s, const TraceDumperOptions &options)
       : m_s(s), m_options(options),
         m_j(m_s.AsRawOstream(),
             /*IndentSize=*/options.pretty_print_json ? 2 : 0) {
     m_j.arrayBegin();
public:
   void DumpInstruction(const TraceDumper::TraceItem &item) {
     m_j.attribute("loadAddress", formatv("{0:x}", item.load_address));
     if (item.symbol_info) {
       m_j.attribute("module", ToOptionalString(GetModuleName(item)));
       m_j.attribute(
           "symbol",
           ToOptionalString(item.symbol_info->sc.GetFunctionName().AsCString()));
 
-      if (item.symbol_info->instruction) {
+      if (lldb::InstructionSP instruction = item.symbol_info->instruction) {
+        ExecutionContext exe_ctx = item.symbol_info->exe_ctx;
         m_j.attribute("mnemonic",
-                      ToOptionalString(item.symbol_info->instruction->GetMnemonic(
-                          &item.symbol_info->exe_ctx)));
+                      ToOptionalString(instruction->GetMnemonic(&exe_ctx)));
+        if (m_options.show_control_flow_kind) {
+          lldb::InstructionControlFlowKind instruction_control_flow_kind =
+              instruction->GetControlFlowKind(&exe_ctx);
+          m_j.attribute("controlFlowKind",
+                        ToOptionalString(
+                            Instruction::GetNameForInstructionControlFlowKind(
+                                instruction_control_flow_kind)));
+        }
       }
 
       if (IsLineEntryValid(item.symbol_info->sc.line_entry)) {
         m_j.attribute(
             "source",
             ToOptionalString(
                 item.symbol_info->sc.line_entry.file.GetPath().c_str()));
         m_j.attribute("line", item.symbol_info->sc.line_entry.line);