Improve `repeat` so it errors if the second argument is a non integer

### Is your feature request related to a problem or challenge?

Prior to https://github.com/apache/datafusion/pull/14268, the following query would error:

```sql
select repeat('-1.2', 3.2);
```

```
query error DataFusion error: Error during planning: Internal error: Expect TypeSignatureClass::Native\(LogicalType\(Native\(Int64\), Int64\)\) but received Float64
```

After https://github.com/apache/datafusion/pull/14268 it appends `3` copies (ignores the `.2` part

```
DataFusion CLI v44.0.0
> select repeat('-1.2', 3.2);
+-----------------------------------+
| repeat(Utf8("-1.2"),Float64(3.2)) |
+-----------------------------------+
| -1.2-1.2-1.2 |
+-----------------------------------+
1 row(s) fetched.
Elapsed 0.023 seconds.
```

### Describe the solution you'd like

Per @jayzhan211 the query should error if the second argument is a non intger: https://github.com/apache/datafusion/pull/14268/files#r1933031384

> I still think non-integer 2nd arg should return error

### Describe alternatives you've considered

_No response_

### Additional context

_No response_

Start by tracing the SQL repeat function and reproduce the reported query, select repeat('-1.2', 3.2), in DataFusion. Confirm that a non-integer second argument now produces an error rather than truncating the value, and add or update coverage for this behavior if the surrounding repeat tests are found.

Written by the indexing model from the issue text.