Merge ECP IdP list from CILogon with local configuration
CILogon keeps a simple list of ECP-enabled IdPs that we can read from to get new members that support that protocol. We also keep a list in our local config.xml so that we don't rely on them entirely (testing, etc). We should merge these.
Duplicates would be determined by the URL and I think we should defer to the CILogon display name since that can be dynamically updated after we release Morpho with a static configuration file into the wild.