reject out-of-range port in SplitHostAndPort

[ubeddulla]

SplitHostAndPort parses the port from a URL or Host header by accumulating digits into a uint64 and narrowing the result with static_cast, with no range check, so a value above INT_MAX silently wraps to a valid-looking but wrong port (":4294967377" becomes 81) and a long run of digits overflows the accumulator. str2endpoint and hostname2endpoint already reject ports outside 0-65535, so this stops accumulating past the range and maps any out-of-range value to -1 to keep the URL parser consistent with them. The added regression test in brpc_uri_unittest.cpp covers the wraparound, the just-over-limit case, a very long digit run, and the Host header path.