Organize additional partner parameters into ADM settings

[jrconlin]

Currently, the ADM settings parameter contains only a filter set, as it is a hash of {partner: {filter settings}}. We should move There are a number of additional partner specific ADM settings that should be moved into this set, since we cannot presume that future partners will have similar settings.

e.g.

adm_settings = {
    "configuration": {
        "endpoint_url": ... ,
        "partner_id": ... ,
        "sub1": ... ,
        "max_tiles": ... ,
        "query_tile_count": ... ,
        "timeout": ... , 
        "ignore_advertisers": ... ,
        "has_legacy_image": ... ,
    }.
    "filters": {
        "ebay":{...}, 
        ...
    }
}
"

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/DISCO-1227)
┆Epic: Extend Shepherd to accommodate more than one partner