[Enhancement] Upgrade CI for PyTorch1.9 (#712)

* Upgrade CI for PyTorch1.9

* fix typo

* merge build_cu101 and build_cu102 to build_cuda

* fix substitution bug

* test

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* remove redudant items

* add python 3.9 to CI

* add python 3.9 to setup.py

* remove some versions of pytorch for python 3.9 test

* fix torch version error

* delete mim files

* update ubuntu version

* fix mmcv cuda version