[AUDIT] Investigate change in "partial results" semantics for JSON read

[mythrocks]

Description
SPARK-40646 introduces a subtle change to how partial parse results are reported when reading JSON input. If the parse on one column fails, the column that follows is also reported as null.

We need to check whether GpuReadJsonFileFormat produces null values in the same way.

Steps/Code to reproduce bug
From the commit message, reading the following input:

{"a": {"x": 1, "y": true}, "b": {"x": 1}}
{"a": {"x": 2}, "b": {"x": 2}}

via the following schema:

val df = spark.read
  .schema("a struct<x: int, y: struct<x: int>>, b struct<x: int>")
  .json("path")

produces the following result:

a	                b
=================================
null	                null
{"x":2,"y":null}	{"x":2}

Expected behavior
The results should have been:

a	                b
=================================
null	                {"x":1}
{"x":2,"y":null}	{"x":2}

Note: This was apparently a regression introduced by SPARK-33134.