* use yapf to format all python file

* yapf exclude two unittests file for they rely on writing and reading file, and format will break them

* disable diff_py_file because too many diff files cause command following failed

Enabled eager_mode for complex unit tests, except for test_complex_op.py and test_complex_view_op.py (#40887)

* rm complexvariable

* modify test_var_base unittest

* remove duplicated codes

* add complex64 and complex128 type; add +-*/@ and slice opreator for complex types

* add test cases for complex elementwise, matmul and getitem unittest

* add test cases for complex types

* add test cases for complex matmul unittest

* Add complex layer for transpose & matmul, test=develop

* Tiny fixes in doc, test=develop

* Fix docs, test=develop

* Init complex number neural network, test=develop

* Improve doc writing, test=develop

* Fix elementwise add & sub, test=develop

* Fix elementwise mul act, test=develop

* a) add ut for complex variable; b) remove arg act in elementwise_ops. test=develop