Inconsistent and incorrect `struct` field coercion

### Describe the bug

When coercing structs with different types DataFusion is inconsistent in its behavior. Sometimes it errors and in other times it is inconsistent

### To Reproduce

Consider two structs with two fields
```sql
create table t as values
(
{ 'foo': 'baz' },
{ 'xxx': arrow_cast('blarg', 'Utf8View') } -- column4 has List of Struct w/ Utf8View and a different field name
);
```

They can be coerced to the same field using `UNION`,

```
> select column1 from t UNION ALL select column2 from t;
+-------------+
| column1 |
+-------------+
| {c0: baz} |
| {c0: blarg} |
+-------------+
2 row(s) fetched.
Elapsed 0.018 seconds.
```

Likewise with `CASE` they are coerced to the same value
```sql
> select CASE WHEN 1=2 THEN column1 ELSE column2 END from t ;
+-----------------------------------------------------------------+
| CASE WHEN Int64(1) = Int64(2) THEN t.column1 ELSE t.column2 END |
+-----------------------------------------------------------------+
| {c0: blarg} |
+-----------------------------------------------------------------+
1 row(s) fetched.
Elapsed 0.010 seconds.
```

### Expected behavior

I believe the field names will be different after
- https://github.com/apache/datafusion/issues/14383
- https://github.com/apache/datafusion/issues/14154

However I expect all of the above queries to fail as the field names are incorrect

I expect the following cases to work:
1. Field names are the same but in different order
2. Field names are the same but the value types need to be coerced themselves (see case on https://github.com/apache/datafusion/issues/14154)

### Additional context

@jayzhan211 suggests: https://github.com/apache/datafusion/pull/14384/files#r1937492704

> Yes, I think type union resolution is the correct on for CASE

Reproduce the UNION and CASE SQL examples from the issue, then trace DataFusion's struct coercion and type-union resolution behavior. Compare the results with the expected cases: reject incompatible field names, while accepting matching names in a different order or with coercible value types; consider the related issues #14383 and #14154.

Written by the indexing model from the issue text.