## What changes were proposed in this pull request?
In the current file source V2 framework, the schema of `FileScan` is not returned correctly if there are overlap columns between `dataSchema` and `partitionSchema`. The actual schema should be
`dataSchema - overlapSchema + partitionSchema`, which might have different column order from the pushed down `requiredSchema` in `SupportsPushDownRequiredColumns.pruneColumns`.
For example, if the data schema is `[a: String, b: String, c: String]` and the partition schema is `[b: Int, d: Int]`, the result schema is `[a: String, b: Int, c: String, d: Int]` in current `FileTable` and `HadoopFsRelation`. while the actual scan schema is `[a: String, c: String, b: Int, d: Int]` in `FileScan`.
To fix the corner case, this PR proposes that the output schema of `FileTable` should be `dataSchema - overlapSchema + partitionSchema`, so that the column order is consistent with `FileScan`.
Putting all the partition columns to the end of table schema is more reasonable.
## How was this patch tested?
Unit test.
Closes#24284 from gengliangwang/FixReadSchema.
Authored-by: Gengliang Wang <gengliang.wang@databricks.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
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