[LLDB] Fix Python GIL-not-held issues

The GIL must be held when calling any Python C API functions. In multithreaded applications that use callbacks this requirement can easily be violated by accident. A general tool to ensure GIL health is not available, but patching Python Py_INCREF to add an assert provides a basic health check:

```
+int PyGILState_Check(void); /* Include/internal/pystate.h */
+
 #define Py_INCREF(op) (                         \
+    assert(PyGILState_Check()),                 \
     _Py_INC_REFTOTAL  _Py_REF_DEBUG_COMMA       \
     ((PyObject *)(op))->ob_refcnt++)

 #define Py_DECREF(op)                                   \
     do {                                                \
+        assert(PyGILState_Check());                     \
         PyObject *_py_decref_tmp = (PyObject *)(op);    \
         if (_Py_DEC_REFTOTAL  _Py_REF_DEBUG_COMMA       \
         --(_py_decref_tmp)->ob_refcnt != 0)             \
```

Adding this assertion causes around 50 test failures in LLDB. Adjusting the scope of things guarded by `py_lock` fixes them.

More background: https://docs.python.org/3/glossary.html#term-global-interpreter-lock

Patch by Ralf Grosse-Kunstleve

Differential Revision: https://reviews.llvm.org/D114722

lldb/source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp

@@ -257,6 +257,7 @@ PythonObject PythonObject::GetAttributeValue(llvm::StringRef attr) const {
 }
 
 StructuredData::ObjectSP PythonObject::CreateStructuredObject() const {
+  assert(PyGILState_Check());
   switch (GetObjectType()) {
   case PyObjectType::Dictionary:
     return PythonDictionary(PyRefType::Borrowed, m_py_obj)