configure: Remove variable noop (thanks shellcheck)

util.async tests: Explicitly import match from luassert (luacheck)

util.startup: Initialize util.async at startup

util.async: Add next-tick configuration Running woken runners in the next iteration of the event loop prevents unexpected recursion, unexpected tracebacks, and is generally more predictable. The pattern is borrowed from util.promise, where we're now doing the same.

util.async: Add sleep() method with configurable scheduling backend No scheduler set by default, so it will error (we plan to initialize it in util.startup). We wanted to avoid a hard dependency on util.timer (which in turn depends on network backends, etc.), and we didn't add timer.sleep() because we didn't want to add a hard dependency on util.async for things that don't need it.

util.stanza: Adjust pretty printing for symmetry Self-closing <tags/> and <?processing instructions?> had some asymmetries in applied colors.

util.dependencies: Discourage Lua 5.1 Search for 'Lua 5.1' for reasons.

util.dependencies: Consider Lua 5.4 Supported:tm: I have been running my own server exclusively on Lua 5.4 for months and apart from packaging issues I remember on major issues.

util.prosodyctl.check: Support direct TLS connectivity checks Currently only supported with OJN Assumption: the direct_tls_ports are not empty when set.

doap: Remove stray ... is that a tab or a space?