Update draft release workflow

[maxrjones]

Description of proposed changes

This PR includes three changes to the draft-release workflow:

1. Replace "actions/upload-release-asset" with "softprops/action-gh-release".
2. Use updated method for setting environment variables in GitHub worklows
3. Separate win32 steps depending on whether it is a full release or release candidate

Fixes #5150

Reminders

• Make sure that your code follows our style. Use the other functions/files as a basis.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Describe changes to function behavior and arguments in a comment below the function declaration.
• If adding new functionality, add a detailed description to the documentation and/or an example.

[seisman]

I can't test it, but it looks good.