add more explains and examples for SELECT ... INTO OUTFILE statements

[qiancai]

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• This PR is translated from: add more explains and examples for SELECT ... INTO OUTFILE statements docs#15104
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[LGTM Timeline notifier]

Timeline:

• 2023-10-31 08:22:40.970242817 +0000 UTC m=+2941358.557352976: ☑️ agreed by ran-huang.

[qiancai]

/approve

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.4: #15527.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #15529.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #15530.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #15531.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.3: #15532.