compose: Expand to take repositories similar to composer

[croissanne]

The only difference with composer here is that the default (pinned) repositories in image-builder-crc would always be included. So this is as an 'extra' repository.

[croissanne]

A request with extra packages could look like this, with the extra repositories included under customizations. @teg wdyt? we could move the extra repositories to the imagerequest itself as well to be more similar to composer?

{
    "distribution": "rhel-85",
    "customizations": {
        "packages": [
            "my_extra_package"
        ],
+        "include_repositories": [
+            {
+                "baseurl": "http://my.extra.repository.com/x86_64/",
+                "rhsm": false (optional; defaults to false)
+            }
+        ]
    },
    "image_requests": [
        {
            "architecture": "x86_64",
            "image_type": "ami",
            "upload_request": {
                "type": "aws",
                "options": {
                    "share_with_accounts": [
                        "012345678912"
                    ]
                }
            }
        }
    ]
}

alternatively

{
    "distribution": "rhel-85",
    "customizations": {
        "packages": [
            "my_extra_package"
        ]
    },
    "image_requests": [
        {
            "architecture": "x86_64",
            "image_type": "ami",
            "upload_request": {
                "type": "aws",
                "options": {
                    "share_with_accounts": [
                        "012345678912"
                    ]
                }
            },
+        "include_repositories": [
+            {
+                "baseurl": "http://my.extra.repository.com/x86_64/",
+                "rhsm": false (optional; defaults to false)
+            }
+        ]
        }
    ]
}

[teg]

Note that we can only do this once we are appropriately security hardened. And we should extend composer to take the extra repos only for the image content, not from the buildroot.

Repos may need to be arch dependent, so either we need to support variables for architecture (maybe that makes sense regardless?) or we need to make them per image request as we do in composer. One could imagine the set of repos being different based on target platform (irrespective of architecture), but considering our idea is that these images should be "the same" except for the low-level bits that we take care of, that might not make sense to expose.