Method readUVarInt32

Fleece/Support/slice_stream.cc:297–306

    __hot
    std::optional<uint32_t> slice_istream::readUVarInt32() noexcept {
        uint32_t n;
        if (size_t bytesRead = GetUVarInt32(*this, &n); bytesRead > 0) {
            skip(bytesRead);
            return n;
        } else {
            return std::nullopt;
        }
    }

}