offload PEP 621 related parsing to standard libraries

[ms-lolo]

https://pep621.readthedocs.io/en/latest/api/pyproject_metadata.html
https://github.com/pypa/pyproject-metadata

this project implements a library for reading PEP 621 compatible metadata from your pyproject.toml. it was approved and folded into the python standard libs in 3.11, so we should switch our custom toml parsing logic to use this package and then simply drop the dependency after we move to >=3.11) across all our projects.

it's not clear if this ticket should wait for poetry 2.0 to be released with its own PEP 621 compatibility changes, but we should adopt this as soon as possible so we can drop a bunch of unstable manual parsing.