Function eval_function_call 

pub fn eval_function_call(
    name: &str,
    call_args: Vec<(Option<String>, Value)>,
    ctx: &EvalContext<'_>,
) -> Result<Value>

Execute a scalar function after its argument expressions have already been evaluated.

This is the shared SQL-semantics kernel used by both the parser AST evaluator and the physical scalar IR evaluator. Keeping dispatch here avoids converting a physical expression back into Expr merely to reuse built-in, sequence, registered, or user-defined function behavior.