API/OP（sequence_first_step，sequence_last_step，sequence_mask，beam_search，beam_search_decode） error message enhancement ,test=release/1.8 (#24668)

* API(dynamic_gru, chunk_eval, BeamSearchDecoder) error message enhancement (#24513)

* dynamic_gru err_msg enhancement, test=develop

* chunk_eval err_msg enhancement and fix crf_decoding output type, test=develop

* BeamSearchDecoder err msg enhancement, test=develop

* API/OP(sequence_expand_as) error message enhancement (#23712) 
Co-authored-by: NGuo Sheng <whucsgs@163.com>

* Format error message for ops, test=release/1.8

* Fix check in sequence_expand, test=release/1.8

* API/OP (Some SL API) error message enhancement  (#24441)

* polish some sl api error message, test=develop

* polish python input check of stride slice, test=develop

* fix unittest bugs, test=develop

* fix error info for transpose sequence_conv_pool max_sequence_len sequ… (#24437)

* fix error info for transpose sequence_conv_pool max_sequence_len sequence_erase, test=develop

* fix error info for transpose sequence_conv_pool max_sequence_len sequence_erase, test=develop

* update modify, test=develop

* update modify, test=develop

* fixed some modifications, test=develop
Co-authored-by: NXing Wu <wuxing03@baidu.com>

* test=develop

* test=develop

* solve the conflict of ops with the same name. test=develop

This reverts commit abe3e690.
test=develop

* solve the conflict of ops with the same name. test=develop

* split some APIs from nn.py to rnn.py

* split some APIs from nn.py to sequence_lod.py

test=develop

* fix unit-test bug

test=develop

* fix test_layers unit-test bug

test=develop