feat: support multple cvssBelow thesholds per version (#2563)

[mwardell-agfa]

Description of Change

Implements the proposed changes in #2563. Adds 3 cvssVnBelow thresholds in the suppression configuration, one for each version (n=2, 3 and 4). The suppression logic is updated so that a vulnerability will only be suppressed if all the version scores are below their cvssVnBelow values. For existing suppressions using cvssBelow nothing changes, only when cvssVnBelow elements are included in the suppression with the new functionality be applied.

For example, in the existing implementation if a vulnerability has a scores of say 5 (V2) and 9 (V3) and cvssBelow is set to 7. The vulnerability is suppressed due to the V2 score of 5. This new functionality will allow a suppression to be configured with cvssV2Below=7, cvssV3Below=7, and then the same vulnerability will not get suppressed since all the cvssBelow checks do not agree to suppress.

Related issues

Fixes #2563

Have test cases been added to cover the new functionality?

yes

[mwardell-agfa]

If there are any additional changes requested or feedback on this, I'd be happy to update the changes to reflect those.

[jeremylong]

I'll need to re-review before I merge - but this will likely be included in the next minor release. I think there might be one more point release before I merge the three feature PRs.