ci: Extend timeout for initial gdbstub commands in panic tests

Theory is that on the runner, in rare cases, gdb may need more than
1 second to load and start responding to commands.

However it's possible these timeouts are due to some other problem
(like gdb failing)

tools/test_apps/system/panic/panic_tests.py

@@ -19,6 +19,7 @@ def test_common(dut, test_name, expected_backtrace=None):
         expected_backtrace = get_default_backtrace(dut.test_name)
 
     if 'gdbstub' in test_name:
+        dut.expect('Entering gdb stub now.')
         dut.start_gdb()
         frames = dut.gdb_backtrace()
         if not dut.match_backtrace(frames, expected_backtrace):