Intermittently failing test

Start with tests/test_autosave.py::test_context_manager_thread_safety and reproduce the Windows CI failure from the linked run. Compare the Autosave-related behavior with epicsdbbuilder issue #32 and PR #177; done means identifying the intermittent cause, making the test pass reliably in CI, and confirming the failure no longer occurs.

There seems to be an intermittent failing test, introduced in the Autosave feature. Here's the failure stack from the last failed run:

   _____________________ test_context_manager_thread_safety ______________________
  Traceback (most recent call last):
    ...
    ...
    File "C:\Users\runneradmin\AppData\Local\Temp\cibw-run-4d5mbdhg\cp39-win_amd64\venv-test\lib\site-packages\_pytest\python.py", line 159, in pytest_pyfunc_call
      result = testfunction(**testargs)
    File "D:\a\pythonSoftIOC\pythonSoftIOC\tests\test_autosave.py", line 443, in test_context_manager_thread_safety
      builder.aOut("PV-FROM-CM")
    File "C:\Users\runneradmin\AppData\Local\Temp\cibw-run-4d5mbdhg\cp39-win_amd64\venv-test\lib\site-packages\softioc\builder.py", line 59, in aOut
      return PythonDevice.ao(name, EGU = EGU, PREC = PREC, **fields)
    File "C:\Users\runneradmin\AppData\Local\Temp\cibw-run-4d5mbdhg\cp39-win_amd64\venv-test\lib\site-packages\softioc\pythonSoftIoc.py", line 117, in __call__
      return RecordWrapper(
    File "C:\Users\runneradmin\AppData\Local\Temp\cibw-run-4d5mbdhg\cp39-win_amd64\venv-test\lib\site-packages\softioc\pythonSoftIoc.py", line 36, in __init__
      record.address = '@' + record.name
    File "C:\Users\runneradmin\AppData\Local\Temp\cibw-run-4d5mbdhg\cp39-win_amd64\venv-test\lib\site-packages\epicsdbbuilder\recordbase.py", line 216, in __setattr__
      self.__ValidateField(fieldname, value)
    File "C:\Users\runneradmin\AppData\Local\Temp\cibw-run-4d5mbdhg\cp39-win_amd64\venv-test\lib\site-packages\epicsdbbuilder\recordbase.py", line 227, in __ValidateField
      self._validate.ValidFieldValue(fieldname, str(value))
    File "C:\Users\runneradmin\AppData\Local\Temp\cibw-run-4d5mbdhg\cp39-win_amd64\venv-test\lib\site-packages\epicsdbbuilder\dbd.py", line 91, in ValidFieldValue
      assert message is None, \
  AssertionError: Can't write "@PV-FROM-CM" to field OUT: fldDes not found

The issue appears to be coming from epicsdbbuilder, which is why I've raised this issue there.

I've attempted to investigate this issue in CI in PR #177 , but have been unable to recreate it so far.