Update and enhance python-gdb.py

Issue #29259:

* Detect PyCFunction is the current frame, not only in the older frame
* Ignore PyCFunction_Call() since it now calls _PyCFunction_FastCallDict(), and
  _PyCFunction_FastCallDict() is already detected
diff --git a/Lib/test/test_gdb.py b/Lib/test/test_gdb.py
index 60f1d92..557591f 100644
--- a/Lib/test/test_gdb.py
+++ b/Lib/test/test_gdb.py
@@ -845,7 +845,7 @@
                                           breakpoint='time_gmtime',
                                           cmds_after_breakpoint=['py-bt-full'],
                                           )
-        self.assertIn('#0 <built-in method gmtime', gdb_output)
+        self.assertIn('#1 <built-in method gmtime', gdb_output)
 
 
 class PyPrintTests(DebuggerTests):