Expand OperServ: SQLINE nick bans, GLOBAL, and KILL

Generalise the network-ban store to carry the ircd X-line kind (defaulted
to the user@host G-line for existing records) so one event-sourced,
lazily-expiring, burst-reasserted list backs every ban type, and drive
ADD/DEL/LIST from one implementation per kind:

- AKILL stays the user@host G-line; SQLINE is a nick Q-line, its mask
  validated as a nick glob (an @ is refused so an AKILL-shaped mask can't
  become an over-broad nick ban). Both are keyed by (kind, mask).
- GLOBAL <message> announces to every user via a $* server-glob notice.
- KILL <nick> [reason] disconnects a user, attributed to the operator.

All four are admin-gated, and OperServ itself stays invisible to non-opers.
Bans and kills go out as typed actions (AddLine/DelLine/KillUser) the ircd
link serialises to ADDLINE/DELLINE/KILL.

inspircd/src/lib.rs

@@ -326,6 +326,7 @@ impl Protocol for InspIrcd {
                 vec![self.sourced(format!("ADDLINE {} {} {} {} {} :{}", kind, mask, setter, now, duration, reason))]
             }
             NetAction::DelLine { kind, mask } => vec![self.sourced(format!("DELLINE {} {}", kind, mask))],
+            NetAction::KillUser { from, uid, reason } => vec![format!(":{} KILL {} :{}", from, uid, reason)],
             NetAction::Raw(s) => vec![s.clone()],
             // Internal: the link layer handles these before serialization.
             NetAction::DeferRegister { .. } | NetAction::DeferPassword { .. } | NetAction::SendEmail { .. } => vec![],