[Enhancement] Rank topn prune redundant rows

[liuyehcf]

What type of PR is this：

• bug
• feature
• enhancement
• refactor
• others

Which issues of this PR fixes ：

Fixes #5885

Enhancement

In previous work #6120, I support rank topn. Comparing to normal topn, rank-topn should take equal range into consideration, but the result is not well-processed, it's result may contain more rows than we need.

For example, given input (1 2 3 3 3 4 5) with limit=3, the expected output should be (1 2 3 3 3), but the actual result may be (1 2 3 3 3)、(1 2 3 3 3 4)、(1 2 3 3 3 4 5), which has the prefix of the expected result and with redundant elements.

Although it's result is not correct, the plan still works fine, because the late full sort and filter will get the correct results.

In this pr, I add pruning mechanism to remove the redundant rows

Change list

• Pruning after done rank topn
• Simplify some conditions of rank topn.
• Add ut for rank topn