sslutil: introduce a function for determining host-specific settings This patch marks the beginning of a series that introduces a new, more configurable, per-host security settings mechanism. Currently, we have global settings (like web.cacerts and the --insecure argument). We also have per-host settings via [hostfingerprints]. Global security settings are good for defaults, but they don't provide the amount of control often wanted. For example, an organization may want to require a particular CA is used for a particular hostname. [hostfingerprints] is nice. But it currently assumes SHA-1. Furthermore, there is no obvious place to put additional per-host settings. Subsequent patches will be introducing new mechanisms for defining security settings, some on a per-host basis. This commits starts the transition to that world by introducing the _hostsettings function. It takes a ui and hostname and returns a dict of security settings. Currently, it limits itself to returning host fingerprint info. We foreshadow the future support of non-SHA1 hashing algorithms for verifying the host fingerprint by making the "certfingerprints" key a list of tuples instead of a list of hashes. We add this dict to the hgstate property on the socket and use it during socket validation for checking fingerprints. There should be no change in behavior.