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/uptrace/bun/migrate/sqlschema/column.go

@@ -0,0 +1,75 @@
+package sqlschema
+
+import (
+	"fmt"
+
+	"github.com/uptrace/bun/schema"
+)
+
+type Column interface {
+	GetName() string
+	GetSQLType() string
+	GetVarcharLen() int
+	GetDefaultValue() string
+	GetIsNullable() bool
+	GetIsAutoIncrement() bool
+	GetIsIdentity() bool
+	AppendQuery(schema.QueryGen, []byte) ([]byte, error)
+}
+
+var _ Column = (*BaseColumn)(nil)
+
+// BaseColumn is a base column definition that stores various attributes of a column.
+//
+// Dialects and only dialects can use it to implement the Column interface.
+// Other packages must use the Column interface.
+type BaseColumn struct {
+	Name            string
+	SQLType         string
+	VarcharLen      int
+	DefaultValue    string
+	IsNullable      bool
+	IsAutoIncrement bool
+	IsIdentity      bool
+	// TODO: add Precision and Cardinality for timestamps/bit-strings/floats and arrays respectively.
+}
+
+func (cd BaseColumn) GetName() string {
+	return cd.Name
+}
+
+func (cd BaseColumn) GetSQLType() string {
+	return cd.SQLType
+}
+
+func (cd BaseColumn) GetVarcharLen() int {
+	return cd.VarcharLen
+}
+
+func (cd BaseColumn) GetDefaultValue() string {
+	return cd.DefaultValue
+}
+
+func (cd BaseColumn) GetIsNullable() bool {
+	return cd.IsNullable
+}
+
+func (cd BaseColumn) GetIsAutoIncrement() bool {
+	return cd.IsAutoIncrement
+}
+
+func (cd BaseColumn) GetIsIdentity() bool {
+	return cd.IsIdentity
+}
+
+// AppendQuery appends full SQL data type.
+func (c *BaseColumn) AppendQuery(gen schema.QueryGen, b []byte) (_ []byte, err error) {
+	b = append(b, c.SQLType...)
+	if c.VarcharLen == 0 {
+		return b, nil
+	}
+	b = append(b, "("...)
+	b = append(b, fmt.Sprint(c.VarcharLen)...)
+	b = append(b, ")"...)
+	return b, nil
+}