[SPARK-48744][Core] Log entry should be constructed only once

[gengliangwang]

What changes were proposed in this pull request?

In the current implementation:

class LogEntry(messageWithContext: => MessageWithContext) {

  def message: String = messageWithContext.message

  def context: java.util.HashMap[String, String] = messageWithContext.context
}

def logInfo(entry: LogEntry): Unit = {
  if (log.isInfoEnabled) {
    withLogContext(entry.context) {
      log.info(entry.message)
    }
  }
}

The field messageWithContext is constructed twice, one from entry.context and another one from entry.message.

This PR is to improve this and ensure a log entry is constructed only once.

Why are the changes needed?

Improve the performance of logging

Does this PR introduce any user-facing change?

No

How was this patch tested?

New UT

Was this patch authored or co-authored using generative AI tooling?

No

[gengliangwang]

cc @panbingkun

[panbingkun]

Perhaps we should put the above testing logic into MDCSuite or a new UT (eg: MessageWithContextSuite), as it seems unrelated to the classification of structured and pattern logs, so it will be executed twice in GA?

[gengliangwang]

A test takes 200ms, running twice is ok. Also, we need to ensure the log entry is constructed only once when structured logging is disabled, too.

[panbingkun]

This is really a great improvement!

[gengliangwang]

Merging to master