[ROCm] Interface changes for StreamExecutor to support both CUDA and ROCm

1) StreamInterface::CudaStreamMemberHack()

Despite the fact that StreamExecutor and GPU common runtime are largely
orthogonal, this particular routine in StreamExecutor is used in GPU common
runtime and a couple of other operators. In this commit it's renamed as
StreamInterface::GpuStreamMemberHack() and their call sites are also changed.

2) StreamExecutorInterface::CudaContextHack()

This member is renamed to StramExecutorInterface::GpuContextHack().

Changes introduced in this commit includes:

- some StreamExecutor interfaces and CUDA implementation
- GPU common runtime related to interface changes in StreamExecutor
- operators affected by interface changes in StreamExecutor