Polish the error message of fc, fused_fc_elementwise_layernorm and fused_embedding_seq_pool. (#27692)

* Polish the error message of fc_op.

* Polish the error message of fused_fc_elementwise_layer_norm op.

* Polish an error message in fused_embedding_seq_pool_op.

* Implement Int8 FC

* Integrate FC into INT8v2

test=develop

* int8 FC: transpose weights before computing scales

test=develop

* Add support for activation_type string in FC

test=develop

* Disable MKL-DNN's FC in VGG16 and 19

test=develop

* Disable FC quantization when mkldnn FC is disabled

test=develop

* Solve PADDLE_ENFORCES in FC int8

* Fix Paddle enforces and remove const cast

test=develop

* Fix style changes

test=develop

* Fix quantizer_tester test and add fc quantization

test=develop

* Fix FC test fail on CUDA

* Remove unnecessary log from quantize placement pass

test=develop

* Add Thread ID to FC hash key

test=develop

* Add comments to MKL-DNN FC Kernel

test=develop

* Refactor quantizer

test=develop

* Fix linter issues

test=develop

* Fix crash in slim googlenet

test=develop

* Fix PADDLE_ENFORCE messages

test=develop

* Add fc padding to solve mkl performance
test=develop

* fix gpu pass and error information
test=develop

* fix fc_fuse_pass_test
test=develop

* fix error information
test=develop

* fix error information
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* fix name and add fc op padding test
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* fix attributes
test=develop

* optimize fc padding
test=develop

* fix test
test=develop

* remove fc_grad, test=develop

* remove fsp op since no unittests, test=develop

* Refine the codes related to fc op.

* Add GPU implementation for fc functor.

* Apply fc_fuse_pass in GPU inference.
test=develop

* Change the cmake for fc op.

* Change PADDLE_ENFORCE to PADDLE_ENFORCE_EQ.

* Add an attribute to set the activation type in fc_op.

* Enhance the unittest of fc_op.
test=develop

* Remove the declaration of FCOpGrad back to the header file.
test=develop

* Set default value for newly added arguments in test_fc_op.
test=develop

test=develop

test=develop

Do not use ctor

* Reduce line of codes.
* We can use virtual function for Maker now.
* The implementation does not care what maker holds, it is easier to
refactor later.