### What changes were proposed in this pull request?

Changed the cost function in CBO to match documentation.

### Why are the changes needed?

The parameter `spark.sql.cbo.joinReorder.card.weight` is documented as:
```
The weight of cardinality (number of rows) for plan cost comparison in join reorder: rows * weight + size * (1 - weight).
```
The implementation in `JoinReorderDP.betterThan` does not match this documentaiton:
```
def betterThan(other: JoinPlan, conf: SQLConf): Boolean = {
      if (other.planCost.card == 0 || other.planCost.size == 0) {
        false
      } else {
        val relativeRows = BigDecimal(this.planCost.card) / BigDecimal(other.planCost.card)
        val relativeSize = BigDecimal(this.planCost.size) / BigDecimal(other.planCost.size)
        relativeRows * conf.joinReorderCardWeight +
          relativeSize * (1 - conf.joinReorderCardWeight) < 1
      }
    }
```

This different implementation has an unfortunate consequence:
given two plans A and B, both A betterThan B and B betterThan A might give the same results. This happes when one has many rows with small sizes and other has few rows with large sizes.

A example values, that have this fenomen with the default weight value (0.7):
A.card = 500, B.card = 300
A.size = 30, B.size = 80
Both A betterThan B and B betterThan A would have score above 1 and would return false.

This happens with several of the TPCDS queries.

The new implementation does not have this behavior.

### Does this PR introduce _any_ user-facing change?

No

### How was this patch tested?

New and existing UTs

Closes #31042 from tanelk/SPARK-33935_cbo_cost_function_3.0.

Authored-by: Tanel Kiis <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>