Fix CUDA extension - Project.toml

[GiggleLiu]

fix #505

In this PR,

• I moved the CUDA extension of YaoToEinsum to CuYao.
• Restored the [weakdeps] and [extensions] sections that removed in a previous commit.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 87.95%. Comparing base (0e44d0d) to head (664ef66). Report is 5 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #506 +/- ## ========================================== + Coverage 87.35% 87.95% +0.59% ========================================== Files 37 88 +51 Lines 2294 5396 +3102 ========================================== + Hits 2004 4746 +2742 - Misses 290 650 +360 ```

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[Roger-luo]

Thanks