Improve SL Micro 6.2 detection

[vzhestkov]

What does this PR do?

SL Micro 6.2 is detected as SLES 16 as it's just a different flavor of SLES 16 the different way as it was with SL Micro 6.1 and previous versions, and provides the following grains:

    os:
        SUSE
    os_family:
        Suse
    osarch:
        x86_64
    oscodename:
        SUSE Linux Enterprise Server 16.0
    osfinger:
        SLES-16
    osfullname:
        SLES
    osmajorrelease:
        16
    osrelease:
        16.0
    osrelease_info:
        - 16
        - 0

This PR improves SL Micro 6.2 detection and provides the following grains instead:

    os:
        SUSE
    os_family:
        Suse
    osarch:
        x86_64
    oscodename:
        SUSE Linux Micro 6.2
    osfinger:
        SL-Micro-6
    osfullname:
        SL-Micro
    osmajorrelease:
        6
    osrelease:
        6.2
    osrelease_info:
        - 6
        - 2

What issues does this PR fix or reference?

Tracks: openSUSE/salt#725

Previous Behavior

SL Micro 6.2 is detected as SLES 16

New Behavior

The grains are aligned with SL Micro 6.1

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• Docs
• Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• Tests written/updated

Commits signed with GPG?

Yes/No