[datafusion-spark] implement spark random functions

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

Implement spark random functions:
- https://spark.apache.org/docs/latest/api/sql/index.html#uniform
- https://spark.apache.org/docs/latest/api/sql/index.html#random
- https://spark.apache.org/docs/latest/api/sql/index.html#rand
- https://spark.apache.org/docs/latest/api/sql/index.html#randn

### Describe the solution you'd like

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### Describe alternatives you've considered

_No response_

### Additional context

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Start with the Spark SQL documentation links in the issue and locate the existing DataFusion Spark function implementations. Implement support for uniform, random, rand, and randn, then verify that the functions behave according to the linked Spark SQL specifications.

Written by the indexing model from the issue text.