Proposal to Improve Severity Mapping in trivy-plugin-sonarqube

[ABK-TMN]

I would like to suggest an improvement to the severity mapping in trivy-plugin-sonarqube.

Currently, the severity mapping is as follows:

TRIVY_SONARQUBE_SEVERITY = {
    "UNKNOWN": "LOW",
    "LOW": "LOW",
    "MEDIUM": "LOW",
    "HIGH": "MEDIUM",
    "CRITICAL": "HIGH",
}

In this mapping, the Trivy severities "MEDIUM" and "HIGH" are mapped to "LOW" and "MEDIUM" in SonarQube, which may reduce severities in the reported vulnerabilities. To address this, I propose the following updated mapping:

TRIVY_SONARQUBE_SEVERITY = {
    "UNKNOWN": "LOW",
    "LOW": "LOW",
    "MEDIUM": "MEDIUM",
    "HIGH": "HIGH",
    "CRITICAL": "HIGH",
}

This revised mapping would ensure a clearer distinction between "MEDIUM" and "HIGH" severities, better aligning Trivy and SonarQube classifications.

[felipewnp]

I would go further and map critical to blocker.