Add support for unstable packages suffixed with vNalpha

[YaseenAlk]

Mentioned this on Slack

It would be helpful if PACKAGE_VERSION_SUFFIX supported unstable package names of the form vNalpha (either by adding patterns v\d+(alpha|beta) and v\d+p\d+(alpha|beta) to the list, or by changing the existing patterns to make the suffixed number optional e.g. v\d+(alpha|beta)\d*). Google APIs calls this channel-based versioning. This would be helpful for the breaking change detector!

Thank you!

[bufdev]

This is done and will go out in the next release (likely today).

[bufdev]

This is released on v0.51.0.