text: Title: bug: inconsistent behavior between `signature_namespace` and `signature_types`
  Body: It's currently difficult to use the simpler `signature_types` syntax in plugins due to the potential of there being an exception raised during startup. 
  
  We should consider removing this entire section to keep the behavior consistent between `signature_namespace` and `signature_types`.
  
  https://github.com/litestar-org/litestar/blob/238d26bab30afa1f852ef0d88830077aab77ba35/tests/unit/test_utils/test_signature.py#L159-L168