### What changes were proposed in this pull request?
This PR changes the behavior of `Column.getItem` to call `Column.getItem` on Scala side instead of `Column.apply`.
### Why are the changes needed?
The current behavior is not consistent with that of Scala.
In PySpark:
```Python
df = spark.range(2)
map_col = create_map(lit(0), lit(100), lit(1), lit(200))
df.withColumn("mapped", map_col.getItem(col('id'))).show()
# +---+------+
# | id|mapped|
# +---+------+
# | 0| 100|
# | 1| 200|
# +---+------+
```
In Scala:
```Scala
val df = spark.range(2)
val map_col = map(lit(0), lit(100), lit(1), lit(200))
// The following getItem results in the following exception, which is the right behavior:
// java.lang.RuntimeException: Unsupported literal type class org.apache.spark.sql.Column id
// at org.apache.spark.sql.catalyst.expressions.Literal$.apply(literals.scala:78)
// at org.apache.spark.sql.Column.getItem(Column.scala:856)
// ... 49 elided
df.withColumn("mapped", map_col.getItem(col("id"))).show
```
### Does this PR introduce any user-facing change?
Yes. If the use wants to pass `Column` object to `getItem`, he/she now needs to use the indexing operator to achieve the previous behavior.
```Python
df = spark.range(2)
map_col = create_map(lit(0), lit(100), lit(1), lit(200))
df.withColumn("mapped", map_col[col('id'))].show()
# +---+------+
# | id|mapped|
# +---+------+
# | 0| 100|
# | 1| 200|
# +---+------+
```
### How was this patch tested?
Existing tests.
Closes#26351 from imback82/spark-29664.
Authored-by: Terry Kim <yuminkim@gmail.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
3175f4bf1b