changed TE 'Allocate' API to take one argument 'Buf' instead of three arguments 'Var', 'dtype', 'dims'. (#50167)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/50167
Test Plan:
Imported from OSS
`python test/test_jit_fuser_te.py`
`python test/test_jit_fuser_legacy.py`
`python test/test_jit_fuser.py`
`build/bin/test_tensorexpr`
Reviewed By: ZolotukhinM
Differential Revision: D25814342
Pulled By: huiguoo
fbshipit-source-id: 44cba7f92365b826c9cb1d385a94858934570dee
