* add stats about duration and padding proportion
* add for utt_duration
* add stats for other recipes
* add stats for other 2 recipes
* modify doc
* minor change
* init files
* use average value as memory vector for each chunk
* change tail padding length from right_context_length to chunk_length
* correct the files, ln -> cp
* fix bug in conv_emformer_transducer_stateless2/emformer.py
* fix doc in conv_emformer_transducer_stateless/emformer.py
* refactor init states for stream
* modify .flake8
* fix bug about memory mask when memory_size==0
* add @torch.jit.export for init_states function
* update RESULTS.md
* minor change
* update README.md
* modify doc
* replace torch.div() with <<
* fix bug, >> -> <<
* use i&i-1 to judge if it is a power of 2
* minor fix
* fix error in RESULTS.md
* copy files from existing branch
* add rule in .flake8
* monir style fix
* fix typos
* add tail padding
* refactor, use fixed-length cache for batch decoding
* copy from streaming branch
* copy from streaming branch
* modify emformer states stack and unstack, streaming decoding, to be continued
* refactor Stream class
* remane streaming_feature_extractor.py
* refactor streaming decoding
* test states stack and unstack
* fix bugs, no grad, and num_proccessed_frames
* add modify_beam_search, fast_beam_search
* support torch.jit.export
* use torch.div
* copy from pruned_transducer_stateless4
* modify export.py
* add author info
* delete other test functions
* minor fix
* modify doc
* fix style
* minor fix doc
* minor fix
* minor fix doc
* update RESULTS.md
* fix typo
* add info
* fix typo
* fix doc
* add test function for conv module, and minor fix.
* add copyright info
* minor change of test_emformer.py
* fix doc of stack and unstack, test case with batch_size=1
* update README.md
