Migrate to `pyproject.toml` and Git versioning

[puddly]

This PR replaces setup.cfg with pyproject.toml, in addition to implementing Git versioning with setuptools-git-versioning.

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (8699553) 99.76% compared to head (665ca19) 99.77%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #568 +/- ## ======================================== Coverage 99.76% 99.77% ======================================== Files 62 67 +5 Lines 4713 4831 +118 ======================================== + Hits 4702 4820 +118 Misses 11 11 ``` | [Impacted Files](https://app.codecov.io/gh/zigpy/bellows/pull/568?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy) | Coverage Δ | | |---|---|---| | [bellows/zigbee/application.py](https://app.codecov.io/gh/zigpy/bellows/pull/568?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy#diff-YmVsbG93cy96aWdiZWUvYXBwbGljYXRpb24ucHk=) | `100.00% <100.00%> (ø)` | | ... and [8 files with indirect coverage changes](https://app.codecov.io/gh/zigpy/bellows/pull/568/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy)

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