Telegram's API and file servers resolve to IPs in the 198.18.0.0/15
range (RFC 2544 benchmarking range). The SSRF filter was blocking these
addresses because ipaddr.js classifies them as 'reserved', and the
filter also had an explicit RFC2544_BENCHMARK_PREFIX check that blocked
them unconditionally.
Fix: exempt 198.18.0.0/15 from the 'reserved' range block in
isBlockedSpecialUseIpv4Address(). Other 'reserved' ranges (TEST-NET-2,
TEST-NET-3, documentation prefixes) remain blocked. The explicit
RFC2544_BENCHMARK_PREFIX check is repurposed as the exemption guard.
Closes#24973
