REALITY client: Clearer log when receiving real certificate

[ari-ahm]

The fmt.Printf call inside UClient's DialTLSContext was executing unconditionally.
This caused log pollution when using xray-core as a library dependency, printing to stdout even when debug mode was disabled.(REALITY localAddr: xxx DialTLSContext)

This patch wraps the print statement with if config.Show, consistent with other debug logs in the file.
This cleans up the output when using the package as a library.

[RPRX]

如果有人看到了这个 log 那说明有福报了 #5066 (comment)

要改成先判断 if show 的话要在外面再加个 error 级别的警报，比如你的连接被重定向了/你正在遭受中间人攻击

[ari-ahm]

I have updated the code based on your feedback.

I added errors.LogError outside the spider loop. This ensures the user receives a clear, high-severity warning about the verification failure (potential MITM/Redirection) exactly once.
I kept the if config.Show guard on the internal DialTLSContext log.

To be honest, the raw DialTLSContext print message didn't mean much to 99% of users and was mostly seen as log spam. By replacing the repetitive prints with a single, clear Error log, we keep the "blessing" of the security warning, but in a format that users can actually understand and act upon.