[BUG] Determine whether it is an `IndexReader` or an `IndexLookUp` error

[qidi1]

Describe the bug

To determine whether it is an IndexReader or an IndexLookUp, the columns in the push-down should be used, not the columns in the predicate and projection. What did you do

  spark.sql("select count(a) from t1").explain()

What do you expect When we judge whether this read is IndexReader use the column a.

What happens instead

When we judge whether this read is IndexReader, the column is empty.

Spark and TiSpark version info

TiSpark: master