[Draft] Add paddle as backend

[HydrogenSulfate]

Modulus Pull Request

Description

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.
• The CHANGELOG.md is up to date with these changes.
• An issue is linked to this pull request.

Dependencies

15/78 tests failed for 13 ModuleNotFoundError(2 pysdf + 11 modulus.sym.models.layers) and 2 ImportError(modulus.models.layers has been moved to modulus but modulus-sym)

============================= test session starts ==============================
platform linux -- Python 3.9.17, pytest-7.4.1, pluggy-1.3.0
rootdir: /workspace/modulus-sym_paddle_backend/test
plugins: hydra-core-1.3.2, anyio-3.7.1, dash-2.13.0
collected 78 items / 15 errors

[HydrogenSulfate]

Hello @ram-cherukuri , thank you for your attention to this PR. Since this PR is only a draft, the code hasn’t been updated for a long time. Therefore, we have temporarily placed the latest code under our own organization: https://github.com/PaddlePaddle/modulus-sym?tab=readme-ov-file#modulus-symbolic-betapaddle-backend.