[SPARK-19544][SQL] Improve error message when some column types are compatible and others are not in set operations

## What changes were proposed in this pull request?

This PR proposes to fix the error message when some data types are compatible and others are not in set/union operation.

Currently, the code below:

```scala
Seq((1,("a", 1))).toDF.union(Seq((1L,("a", "b"))).toDF)
```

throws an exception saying `LongType` and `IntegerType` are incompatible types. It should say something about `StructType`s with more readable format as below:

**Before**

```
Union can only be performed on tables with the compatible column types.
LongType <> IntegerType at the first column of the second table;;
```

**After**

```
Union can only be performed on tables with the compatible column types.
struct<_1:string,_2:string> <> struct<_1:string,_2:int> at the second column of the second table;;
```

*I manually inserted a newline in the messages above for readability only in this PR description.

## How was this patch tested?

Unit tests in `AnalysisErrorSuite`, manual tests and build wth Scala 2.10.

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #16882 from HyukjinKwon/SPARK-19544.

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