Added support for the non-zero inputs of hidden state and cell state for LSTM layer as requested in issue #19278 (part 1). ONNX and TF importers are supported.

Test data here: opencv/opencv_extra#886

opencv_extra=lstm_inside

I was unable to add the tests for TensorFlow 2 because of the known issue: tensorflow/tensorflow#47554

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under Apache 2 License.
• To the best of my knowledge, the proposed patch is not based on a code under GPL or other license that is incompatible with OpenCV
• The PR is proposed to proper branch
• There is reference to original bug report and related work
• There is accuracy test, performance test and test data in opencv_extra repository, if applicable
  Patch to opencv_extra has the same branch name.
• The feature is well documented and sample code can be built with the project CMake