cmake: Add debugger

- Depends on cppdap and jsoncpp.
- Add --debugger argument to enable the Debugger.
- Add --debugger-pipe argument for DAP traffics over named pipes.
- Support breakpoints by filenames and line numbers.
- Support exception breakpoints.
- Call stack shows filenames and line numbers.
- Show Cache Variables.
- Show the state of currently defined targets,
  tests and directories with their properties.
- Add cmakeVersion to DAP initialize response.
- Include unit tests.

Co-authored-by: Ben McMorran <bemcmorr@microsoft.com>

Source/cmDebuggerThread.h

@@ -0,0 +1,59 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#pragma once
+
+#include "cmConfigure.h" // IWYU pragma: keep
+
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+#include <mutex>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include <cm3p/cppdap/protocol.h>
+
+class cmListFileFunction;
+class cmMakefile;
+
+namespace cmDebugger {
+class cmDebuggerStackFrame;
+class cmDebuggerVariables;
+class cmDebuggerVariablesManager;
+}
+
+namespace cmDebugger {
+
+class cmDebuggerThread
+{
+  int64_t Id;
+  std::string Name;
+  std::vector<std::shared_ptr<cmDebuggerStackFrame>> Frames;
+  std::unordered_map<int64_t, std::shared_ptr<cmDebuggerStackFrame>> FrameMap;
+  std::mutex Mutex;
+  std::unordered_map<int64_t, std::vector<dap::Scope>> FrameScopes;
+  std::unordered_map<int64_t,
+                     std::vector<std::shared_ptr<cmDebuggerVariables>>>
+    FrameVariables;
+  std::shared_ptr<cmDebuggerVariablesManager> VariablesManager;
+
+public:
+  cmDebuggerThread(int64_t id, std::string name);
+  int64_t GetId() const { return this->Id; }
+  const std::string& GetName() const { return this->Name; }
+  void PushStackFrame(cmMakefile* mf, std::string const& sourcePath,
+                      cmListFileFunction const& lff);
+  void PopStackFrame();
+  std::shared_ptr<cmDebuggerStackFrame> GetTopStackFrame();
+  std::shared_ptr<cmDebuggerStackFrame> GetStackFrame(int64_t frameId);
+  size_t GetStackFrameSize() const { return this->Frames.size(); }
+  dap::ScopesResponse GetScopesResponse(int64_t frameId,
+                                        bool supportsVariableType);
+  dap::VariablesResponse GetVariablesResponse(
+    dap::VariablesRequest const& request);
+  friend dap::StackTraceResponse GetStackTraceResponse(
+    std::shared_ptr<cmDebuggerThread> const& thread);
+};
+
+} // namespace cmDebugger