Move metadata from non-standard setup.cfg into PEP 621-compliant pyproject.toml. (546 takeover)

[BradleySappington]

Move metadata from non-standard setup.cfg into PEP 621-compliant pyproject.toml remove setup.py and setup.cfg

[codecov[bot]]

Codecov Report

Patch coverage: 94.73% and no project coverage change.

Comparison is base (c95c578) 73.97% compared to head (4dab745) 73.97%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #561 +/- ## ======================================== Coverage 73.97% 73.97% ======================================== Files 18 18 Lines 6612 6612 ======================================== Hits 4891 4891 Misses 1721 1721 ``` | [Impacted Files](https://app.codecov.io/gh/spacetelescope/poppy/pull/561?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spacetelescope) | Coverage Δ | | |---|---|---| | [poppy/\_\_init\_\_.py](https://app.codecov.io/gh/spacetelescope/poppy/pull/561?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spacetelescope#diff-cG9wcHkvX19pbml0X18ucHk=) | `98.00% <94.73%> (ø)` | |

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[BradleySappington]

thanks to @KOLANICH for initial submission!

[BradleySappington]

Ready for Review @ojustino @obi-wan76

[BradleySappington]

All feedback submitted! Thanks @KOLANICH and @zacharyburnett for the extra eyes

[ojustino]

Hi @BradleySappington, I can take a look by tomorrow if @obi-wan76 doesn't get to it more quickly. It seems like the branch is in a good place at first glance.