Introduce CompactedRow

[luoyuxia]

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• I searched in the issues and found nothing similar.

Description

refer to https://github.com/apache/fluss/blob/main/fluss-common/src/main/java/org/apache/fluss/row/compacted/CompactedRow.java

Willingness to contribute

• I'm willing to submit a PR!

[Kelvinyu1117]

I would like to take this task if no one is working on it at the moment.

[luoyuxia]

Thanks

[luoyuxia]

@Kelvinyu1117 FYI. I found this task may be bigger, to make it more trackable. I create a task #118 to track write compacted row. So, in this task, we just need introduce CompactedRow and CompactedRowReader

[Kelvinyu1117]

Sure, I am actually implementing these two structures.

[luoyuxia]

Sure, I am actually implementing these two structures.

That's great. You can submit a pr for #118 firstly.