Fix /etc/redhat-release file parsing when resolving distro details

[wagoodman]

Description

It seems that parsing /etc/redhat-release files results in the wrong values in some cases:

$ syft localhost/testimage:latest -o json | jq '.distro'

{
  "prettyName": "Red Hat Enterprise Linux",
  "name": "red hat enterprise linux",
  "id": "red hat enterprise linux",
  "idLike": [
    "red hat enterprise linux"
  ],
  "version": "8.10",
  "versionID": "8.10"
}

This PR adjusts the values to be more inline with expected values:

{
  "prettyName": "Red Hat Enterprise Linux release 8.10 (Ootpa)",
  "name": "Red Hat Enterprise Linux",
  "id": "rhel",
  "idLike": [
    "rhel"
  ],
  "version": "8.10 (Ootpa)",
  "versionID": "8.10"
}

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have added unit tests that cover changed behavior
• I have tested my code in common scenarios and confirmed there are no regressions
• I have added comments to my code, particularly in hard-to-understand sections