feat(bun): generate native Go array slices for PostgreSQL array columns

Bun's pgdialect scans/appends native slices directly, so array columns
(text[], integer[], uuid[], ...) always generate as plain []string,
[]int32, etc. with an explicit "array" bun tag, regardless of --types
(sqltypes/stdlib/baselib). The SqlXxxArray wrapper types are no longer
used for Bun array columns (gorm is unaffected and keeps using them).

Adds --array-nullable pointer_slice to represent nullable array columns
as *[]T instead of []T, so callers can distinguish SQL NULL (nil) from
'{}' (pointer to an empty slice). Verified end-to-end against a live
PostgreSQL instance for NULL/{}/populated arrays in every --types mode.

Closes #13

vendor/github.com/jackc/puddle/v2/internal/genstack/stack.go

@@ -0,0 +1,39 @@
+package genstack
+
+// stack is a wrapper around an array implementing a stack.
+//
+// We cannot use slice to represent the stack because append might change the
+// pointer value of the slice. That would be an issue in GenStack
+// implementation.
+type stack[T any] struct {
+	arr []T
+}
+
+// push pushes a new element at the top of a stack.
+func (s *stack[T]) push(vs ...T) { s.arr = append(s.arr, vs...) }
+
+// pop pops the stack top-most element.
+//
+// If stack length is zero, this method panics.
+func (s *stack[T]) pop() T {
+	idx := s.len() - 1
+	val := s.arr[idx]
+
+	// Avoid memory leak
+	var zero T
+	s.arr[idx] = zero
+
+	s.arr = s.arr[:idx]
+	return val
+}
+
+// takeAll returns all elements in the stack in order as they are stored - i.e.
+// the top-most stack element is the last one.
+func (s *stack[T]) takeAll() []T {
+	arr := s.arr
+	s.arr = nil
+	return arr
+}
+
+// len returns number of elements in the stack.
+func (s *stack[T]) len() int { return len(s.arr) }