Clean up Handling of Dev Versions

[blink1073]

Problem

Our current handling of .dev versions is awkward.
It is unclear which version spec to use, and the setting is manual in the Full Release workflow.

Proposed Solution

Get the current version from the changelog instead of the package itself. This allows next, patch, etc. to work from that version.
Instead of post version spec, have a setting for the dev version: None, patch, or minor. It will automatically be applied.

Additional context

This will be needed for #272

[blink1073]

Fixed by #287