support to run example/test.py on Arm

[TianyuLi0]

• Add pytorch requirement for Arm CPU, link to th_transformer
• Integrate sampleGreedy from Haijiang
• Add tracker allocator for Arm device
• Add cpu support for start server function
• Using the commom parallel_for for Arm sample operation
• Fix integration issues

To run the example: bazel test //example:test --config=arm --test_output=all