feat(maven): add `mirrors` support for settings.xml files

Description

We have already added repository retrieval from the profiles field. But Trivy should also check mirrors.

    <mirrors>
        <mirror>
            <id>mycompany-maven-central-mirror</id>
            <name>mycompany-maven-central-mirror</name>
            <url>https://mycompany.example.com/repository/maven-central-mirror</url>
            <mirrorOf>central</mirrorOf>
        </mirror>
    </mirrors>