mod_pubsub_serverinfo: implemented all basic features This commit replaces the earlier proof-of-concept to a solution that: - reports on remotely-connected domains - uses disco/info to detect if those domains opt-in - publishes domain names for remote domains that do so - caches the disco/info response

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summary: Set process name to prosody
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This module sets the process name to `prosody` so it shows up as such
instead of `lua` in process management tools.

To use this module, you'll need the proctitle Lua library:
<https://github.com/hoelzro/lua-proctitle>