[CH] Diff when cast double/float to string

### Backend

CH (ClickHouse)

### Bug description

`select cast(21.0d as string);`

expected result is `21.0`, but return `21`

### Spark version

Spark-3.3.x

### Spark configurations

_No response_

### System information

_No response_

### Relevant logs

_No response_

Start by reproducing `select cast(21.0d as string);` in the ClickHouse backend on Spark 3.3.x, then trace the cast-to-string handling for floating-point values. Done means the query returns `21.0` rather than `21`, with regression coverage for this case.

Written by the indexing model from the issue text.