util.session: Add role management methods

net.connect: Clear TODO for Happy Eyeballs / RFC 8305, close #1246 Gotta have the DOAP references!

Merge 0.12->trunk

mod_admin_shell: Switch names for user role management commands user:roles() does not convey that this is the mutating command, it should have been called setroles from the start but wasn't due to lack of foresight. This has to accidentally removing roles when wanting to show them.

util.stanza: Add method for extracting a single attribute value Sometimes you only care about a single attribute, but the child tag itself may be optional, leading to needing `tag and tag.attr.foo` or `stanza:find("tag@foo")`. The `:find()` method is fairly complex, so avoiding it for this kind of simpler use case is a win.

mod_time: Remove obsolete XEP-0090 support Deprecated even before Prosody even started, obsolete for over a decade.

util.datetime: Update Teal interface description Integers were required before, now any number should work.

util.datetime: Remove a line No idea why the locals were declared on a line by itself. Perhaps line length considerations? But saving 6 characters in width by adding a whole line with 47 characters seems excessive. This is still within the 150 character limit set by .luacheckrc

mod_time: Return sub-second precision timestamps Because why not? Who even has this module enabled?

mod_storage_sql: Drop archive timestamp precision pending schema update The "when" column is an INTEGER which will probably be unhappy about storing higher precision timestamps, so we keep the older behavior for now.