rework build matrix to a single workflow

[altendky]

This closely follows the form of Chia-Network/chiavdf#118.

Draft for:

• Perhaps do the sdist separately as in other workflows.
• Consider needs: for checks.
• Also install wheel in Windows.
• Do we need to build for multiple Python versions? eae4d94 catch up merge completed excluding these changes. Can be recovered if discussion leads there.
  • Yes, we do need it as we no longer build with abi3 since we want to use the buffer protocol.