Import upstream v0.16.25, stripped

Upstream commit: 3f657330c0f49a015a3a372fb59669b5cccbca6d
Enterprise-only files removed or emptied: 63
Enterprise-only snippets removed: 118 in 50 files
Dangling module declarations removed: 5
Edits turning enterprise off: 25
Third-party code: 14 files, 0 not in THIRD-PARTY.md
Renamed identifiers: 67 in 19 files
Verification: clean

The same Enterprise footprint as v0.16.24. The build check is clean
apart from the expected errors in the rebuilt-feature tests. A
bug-fix release: DKIM rotation, IMAP failed-login answers, DNSBL
multi-code scoring and negative TTLs, Pyzor on short messages, queue
quotas with an empty match, RocksDB info-log rotation, and
Autodiscover schema handling.

tests/src/utils/dns.rs

@@ -77,14 +77,12 @@ impl DnsCache for Server {
     fn dnsbl_add(&self, name: &str, value: Vec<Ipv4Addr>, valid_until: std::time::Instant) {
         self.inner.cache.dns_rbl.insert_with_expiry(
             name.into(),
-            Some(Arc::new(IpResolver::new(
+            Some(
                 value
-                    .iter()
-                    .copied()
-                    .next()
-                    .unwrap_or(Ipv4Addr::BROADCAST)
-                    .into(),
-            ))),
+                    .into_iter()
+                    .map(|ip| IpResolver::new(ip.into()))
+                    .collect(),
+            ),
             valid_until,
         );
     }