Move stats into expr (#5582)

Just a reminder, the end state is:

```
vortex-expr/
  stats
  scalar_fn
  Expr
  
vortex-array -> vortex-expr
  ScalarFnArray
  
vortex-layout -> vortex-expr
  ScalarFnLayout
```

Where Expr becomes a closed enum with almost all logic implemented via
ScalarFn.

---------

Signed-off-by: Nicholas Gates <[email protected]>

Author: gatesn

encodings/datetime-parts/src/compute/take.rs

@@ -9,8 +9,8 @@ use vortex_array::compute::TakeKernel;
 use vortex_array::compute::TakeKernelAdapter;
 use vortex_array::compute::fill_null;
 use vortex_array::compute::take;
+use vortex_array::expr::stats::Stat;
 use vortex_array::register_kernel;
-use vortex_array::stats::Stat;
 use vortex_array::stats::StatsProvider;
 use vortex_dtype::Nullability;
 use vortex_error::VortexResult;

encodings/fastlanes/src/for/array/for_compress.rs

@@ -5,7 +5,7 @@ use num_traits::PrimInt;
 use num_traits::WrappingSub;
 use vortex_array::IntoArray;
 use vortex_array::arrays::PrimitiveArray;
-use vortex_array::stats::Stat;
+use vortex_array::expr::stats::Stat;
 use vortex_dtype::NativePType;
 use vortex_dtype::match_each_integer_ptype;
 use vortex_error::VortexResult;

encodings/runend/src/compute/is_constant.rs

@@ -6,8 +6,8 @@ use vortex_array::compute::IsConstantKernel;
 use vortex_array::compute::IsConstantKernelAdapter;
 use vortex_array::compute::IsConstantOpts;
 use vortex_array::compute::is_constant_opts;
+use vortex_array::expr::stats::Stat;
 use vortex_array::register_kernel;
-use vortex_array::stats::Stat;
 use vortex_error::VortexResult;
 
 use crate::RunEndVTable;

vortex-array/src/array/mod.rs

@@ -50,10 +50,10 @@ use crate::compute::InvocationArgs;
 use crate::compute::IsConstantOpts;
 use crate::compute::Output;
 use crate::compute::is_constant_opts;
+use crate::expr::stats::Stat;
 use crate::hash;
 use crate::serde::ArrayChildren;
 use crate::stats::Precision;
-use crate::stats::Stat;
 use crate::stats::StatsProviderExt;
 use crate::stats::StatsSetRef;
 use crate::vtable::ArrayId;

vortex-array/src/arrays/constant/compute/sum.rs

@@ -24,8 +24,8 @@ use crate::arrays::ConstantArray;
 use crate::arrays::ConstantVTable;
 use crate::compute::SumKernel;
 use crate::compute::SumKernelAdapter;
+use crate::expr::stats::Stat;
 use crate::register_kernel;
-use crate::stats::Stat;
 
 impl SumKernel for ConstantVTable {
     fn sum(&self, array: &ConstantArray, accumulator: &Scalar) -> VortexResult<Scalar> {
@@ -184,7 +184,7 @@ mod tests {
     use crate::arrays::ConstantArray;
     use crate::compute::sum;
     use crate::compute::sum_with_accumulator;
-    use crate::stats::Stat;
+    use crate::expr::stats::Stat;
 
     #[test]
     fn test_sum_unsigned() {

vortex-array/src/arrays/constant/vtable/canonical.rs

@@ -336,7 +336,7 @@ mod tests {
     use crate::arrays::ConstantArray;
     use crate::arrays::ListViewRebuildMode;
     use crate::canonical::ToCanonical;
-    use crate::stats::Stat;
+    use crate::expr::stats::Stat;
     use crate::stats::StatsProvider;
     use crate::validity::Validity;
     use crate::vtable::ValidityHelper;

vortex-array/src/arrays/decimal/compute/sum.rs

@@ -21,8 +21,8 @@ use crate::arrays::DecimalArray;
 use crate::arrays::DecimalVTable;
 use crate::compute::SumKernel;
 use crate::compute::SumKernelAdapter;
+use crate::expr::stats::Stat;
 use crate::register_kernel;
-use crate::stats::Stat;
 
 impl SumKernel for DecimalVTable {
     #[expect(

vortex-array/src/arrays/varbin/compute/min_max.rs

@@ -70,7 +70,7 @@ mod tests {
     use crate::arrays::VarBinArray;
     use crate::compute::MinMaxResult;
     use crate::compute::min_max;
-    use crate::stats::Stat;
+    use crate::expr::stats::Stat;
     use crate::stats::StatsProvider;
 
     #[test]

vortex-array/src/compute/is_constant.rs

@@ -22,8 +22,8 @@ use crate::compute::InvocationArgs;
 use crate::compute::Kernel;
 use crate::compute::Options;
 use crate::compute::Output;
+use crate::expr::stats::Stat;
 use crate::stats::Precision;
-use crate::stats::Stat;
 use crate::stats::StatsProvider;
 use crate::stats::StatsProviderExt;
 use crate::vtable::VTable;
@@ -307,7 +307,7 @@ mod tests {
 
     use crate::IntoArray as _;
     use crate::arrays::PrimitiveArray;
-    use crate::stats::Stat;
+    use crate::expr::stats::Stat;
 
     #[test]
     fn is_constant_min_max_no_nan() {

vortex-array/src/compute/is_sorted.rs

@@ -22,8 +22,8 @@ use crate::compute::InvocationArgs;
 use crate::compute::Kernel;
 use crate::compute::Options;
 use crate::compute::Output;
+use crate::expr::stats::Stat;
 use crate::stats::Precision;
-use crate::stats::Stat;
 use crate::stats::StatsProviderExt;
 use crate::vtable::VTable;