Create gentoo imporver to handel revisione versions correctly

> the gentoo version documentation https://projects.gentoo.org/pms/8/pms.html#x1-250003.2. It turns out that gentoo packages do not follow any particular versioning standard, so it becomes difficult to create a range from a single version such that the range includes only revisions of that version.
>
> The only reliable way to generate a bounded range for a revisione version is to retrieve all versions of a particular gentoo package and sort them as described here https://projects.gentoo.org/pms/8/pms.html#x1-260003.3 and then select the last revision of that version as the terminating bound.
>

Per @keshav-space :
- https://github.com/aboutcode-org/vulnerablecode/pull/2090#discussion_r2823984652

So, we should have an improver that handles this correctly.