feat(go/adbc/driver/bigquery): add BIGQUERY:type field metadata (#3604)

## Motivation
The `Type` metadata key has two limitations which stems from BigQuery's
API:
1. it says fields of type `ARRAY<T>` are just `T` with `Repeated=true`
2. it says `STRUCT<...>` fields are simply `RECORD`, and erases any
information about the inner fields.

These limitations can cause problems when trying to parse the `Type` key
or when using it verbatim against the warehouse in a statement, e.g a
`CREATE TABLE` statement or a `AS T` cast.

## Summary
This PR adds a new `BIGQUERY:type` key that formats the original SQL
string as [specified by
BigQuery](https://cloud.google.com/bigquery/docs/reference/standard-sql/data-types#declaring_a_struct_type).

Most types remain unchanged as they come from `gobigquery`, and in those
cases this key will contain the same value as `Type`.

However, arrays and structs get transformed to match the richer type
string.

## Testing
I ran a `CREATE TABLE AS` query against BigQuery. Here's the result for
fields of different types

[1] Regular non-nested types are simply copied over from the value of
`Type`
<details>
<summary>1</summary>
<img width="331" height="1071" alt="image"
src="https://github.com/user-attachments/assets/ccd2ce17-37d8-4630-bef5-a503ed450c2a"
/>
</details>

[2] An array of integers becomes `ARRAY<INTEGER>`, while `Type` remains
`INTEGER`
<details>
<summary>2</summary>
<img width="319" height="369" alt="image"
src="https://github.com/user-attachments/assets/e588d7ac-c7ca-40fb-ab51-9795e566d240"
/>
</details>

[3] An array of structs becomes `ARRAY<STRUCT<...>>`
<details>
<summary>3</summary>
<img width="551" height="816" alt="image"
src="https://github.com/user-attachments/assets/bb946ebc-747a-4529-88a8-68636f94e44e"
/>
</details>

[4] A struct of arrays' inner types are `ARRAY<...>`
<details>
<summary>4</summary>
<img width="610" height="922" alt="image"
src="https://github.com/user-attachments/assets/932a3554-ea56-4b1f-8642-801ee91c4f63"
/>
</details>

[5] A deeply nested struct also has the correct inner types
<details>
<summary>5</summary>
<img width="1327" height="1307" alt="image"
src="https://github.com/user-attachments/assets/3185651b-8809-42b0-adc4-ec956eaf9e87"
/>
</details>

## Related issues
- #3449

Author: serramatutu

go/adbc/driver/bigquery/connection.go

@@ -795,6 +795,8 @@ func buildField(schema *bigquery.FieldSchema, level uint) (arrow.Field, error) {
 	field.Nullable = !schema.Required
 	metadata["Type"] = string(schema.Type)
 
+	richSqlType := string(schema.Type)
+
 	if schema.PolicyTags != nil {
 		policyTagList, err := json.Marshal(schema.PolicyTags)
 		if err != nil {
@@ -823,14 +825,21 @@ func buildField(schema *bigquery.FieldSchema, level uint) (arrow.Field, error) {
 	case bigquery.RecordFieldType:
 		// create an Arrow struct for BigQuery Record fields
 		nestedFields := make([]arrow.Field, len(schema.Schema))
+		nestedRichSqlTypes := make([]string, len(schema.Schema))
 		for i, nestedFieldSchema := range schema.Schema {
 			f, err := buildField(nestedFieldSchema, level+1)
 			if err != nil {
 				return arrow.Field{}, err
 			}
 			nestedFields[i] = f
+
+			fieldRichSqlType, found := f.Metadata.GetValue("BIGQUERY:type")
+			if found {
+				nestedRichSqlTypes[i] = fmt.Sprintf("`%s` %s", f.Name, fieldRichSqlType)
+			}
 		}
 		structType := arrow.StructOf(nestedFields...)
+		richSqlType = fmt.Sprintf("STRUCT<%s>", strings.Join(nestedRichSqlTypes, ", "))
 		if structType == nil {
 			return arrow.Field{}, adbc.Error{
 				Code: adbc.StatusInvalidArgument,
@@ -888,8 +897,12 @@ func buildField(schema *bigquery.FieldSchema, level uint) (arrow.Field, error) {
 	// if the field is repeated, then it's a list of the type we just built
 	if schema.Repeated {
 		field.Type = arrow.ListOf(field.Type)
+		richSqlType = fmt.Sprintf("ARRAY<%s>", richSqlType)
 	}
 
+	// derive the standard type string from the field
+	metadata["BIGQUERY:type"] = richSqlType
+
 	if level == 0 {
 		metadata["DefaultValueExpression"] = schema.DefaultValueExpression
 	}