* refactor eager flags

* fix flags error when we switch from eager to dygraph

* fix ci problem

* fix ci

* fix ci

* merge develop and fix code style

* merge develop and fix code style

* fix op test error

* fix op test error

* fix op test error

* fix op test error

* fix op test error

* merge develop

* fix typos: is_integer in attribute.py
* add more test cases for fft

2. add complex data type support for paddle.shape at graph assembly.

* fix fftshift/ifftshift on static mode
* update roll_op version
* add more test cases for fftshift/ifftshift

* move signal apis

* move fft.py and signal.py to paddle/, fix typos

* fix relative imports from fft.py and signal.py

* fix typos

* update fft api path
* add sample code for ihfft2
Co-authored-by: Nchenfeiyu <chenfeiyu@baidu.com>