distro/rhel8: use azure-rhui pkg set and image config for vhd

Extract the non-RHUI specific package set and image configuration into a
common definitions, which will be used by both image types.

Redefine the package sets and default image configuration used by both
image types to inherit from a common definition.

Regenerate image manifests for RHEL-8 / c8s `vhd` and `azure-rhui`
images.

There is no change in the resulting manifest for the `azure-rhui` image
type. However there are substantial changes to the `vhd` image
definition, which is now almost identical to the `azure-rhui` image
type, to provide consistent experience regardless if using RHUI or not.

The default partition table used by the `vhd` image type has been kept
as it was before, since there is yet no consensus on what size to
standardize for both image types.

test/data/manifests/rhel_8-x86_64-azure_rhui-boot.json

@@ -13336,6 +13336,5 @@
         "checksum": "sha256:10e429e047cea577ade1d52422a39af6349b4427b6aba8865dc4eba169c142ce"
       }
     ]
-  },
-  "no-image-info": true
+  }
 }

test/data/manifests/rhel_84-x86_64-azure_rhui-boot.json

@@ -13462,6 +13462,5 @@
         "checksum": "sha256:10e429e047cea577ade1d52422a39af6349b4427b6aba8865dc4eba169c142ce"
       }
     ]
-  },
-  "no-image-info": true
+  }
 }

test/data/manifests/rhel_85-x86_64-azure_rhui-boot.json

@@ -13354,6 +13354,5 @@
         "checksum": "sha256:10e429e047cea577ade1d52422a39af6349b4427b6aba8865dc4eba169c142ce"
       }
     ]
-  },
-  "no-image-info": true
+  }
 }

test/data/manifests/rhel_86-x86_64-azure_rhui-boot.json

@@ -13336,6 +13336,5 @@
         "checksum": "sha256:10e429e047cea577ade1d52422a39af6349b4427b6aba8865dc4eba169c142ce"
       }
     ]
-  },
-  "no-image-info": true
+  }
 }

test/data/manifests/rhel_87-x86_64-azure_rhui-boot.json

@@ -13336,6 +13336,5 @@
         "checksum": "sha256:10e429e047cea577ade1d52422a39af6349b4427b6aba8865dc4eba169c142ce"
       }
     ]
-  },
-  "no-image-info": true
+  }
 }