User defined functions (udf) documentation improvements

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

Try be more consistent with the generated docs for our UDFs

### Describe the solution you'd like

- [ ] lint/format the docs, such as ensuring the sql example is well formatted
- https://github.com/apache/datafusion/blob/bc48a4f7acd87a9779cb5a88d9b1a3f4ce506e45/docs/source/user-guide/sql/scalar_functions.md?plain=1#L5819-L5824
- see how last `|` is offset
- [ ] ensure argument names have consistent format (e.g. disallow `-`, prefer `_`)
- [ ] some way to check that argument names match whats in the syntax example
- better yet, is there a way to auto generate the syntax examples from the arguments? we'd need a way to get the function name, and a way to mark arguments as optional
- [ ] anything else?

### Describe alternatives you've considered

_No response_

### Additional context

Related:

- https://github.com/apache/datafusion/pull/24134

Start with the scalar function documentation excerpt in docs/source/user-guide/sql/scalar_functions.md around lines 5819-5824, then review the related pull request #24134. Compare the generated UDF examples and argument names across the docs; the work is done when the formatting and naming are consistent and the documented syntax matches the function arguments.

Written by the indexing model from the issue text.