[revert] recover "[refactor] restructure configuration files (#2977)"

[FrankLeeeee]

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partial fix for #3012 fixed #3016

📝 What does this PR do?

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This PR fixed the PyTorch not found error during installation. The root cause is the usage of pyproject.toml. Despite the fact that pyproject.toml is a newer version of python build tool, it introduces some new features which conflict with our setup.py. The underlying reason for the bug is that pyproject.toml will execute python build in an isolated environment. As a result, PyTorch cannot be found in this isolated environment, leading to installation error when CUDA_EXT=1 is provided.

There is no easy solution to fix this according to https://github.com/pypa/pip/issues/6144. Thus, it might be just good to revert this commit.

Since #3017 is related to pyproject.toml, I will just close #3017 .

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