* add ldexp api

* fix ldexp

* Update math.py

fix math.py

* rewrite the ldexp

* Simplify ldexp implementation

* fix codestyle

* Update math.py

* Update math.py

* modify the test_ldexp.py

* fix the input bug of np.ldexp

* fix the bug of np.ldexp in windows

* modify the ldexp function and add the dtype check of output

* Update test_ldexp.py

* fix the dtype

* fix codestyle

* Update python/paddle/tensor/math.py

add note for code description
Co-authored-by: Nzachary sun <70642955+sunzhongkai588@users.noreply.github.com>

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Co-authored-by: Nzachary sun <70642955+sunzhongkai588@users.noreply.github.com>