Related to #42148
Add comprehensive support for struct array field type in the Go SDK,
including data structure definitions, column operations, schema
construction, and full test coverage.
**Struct Array Column Implementation (`client/column/struct.go`)**
- Add `columnStructArray` type to handle struct array fields
- Implement `Column` interface methods:
- `NewColumnStructArray()`: Create new struct array column from
sub-fields
- `Name()`, `Type()`: Basic metadata accessors
- `Slice()`: Support slicing across all sub-fields
- `FieldData()`: Convert to protobuf `StructArrayField` format
- `Get()`: Retrieve struct values as `map[string]any`
- `ValidateNullable()`, `CompactNullableValues()`: Nullable support
- Placeholder implementations for unsupported operations (AppendValue,
GetAsX, IsNull, AppendNull)
**Struct Array Parsing (`client/column/columns.go`)**
- Add `parseStructArrayData()` function to parse `StructArrayField` from
protobuf
- Update `FieldDataColumn()` to detect and parse struct array fields
- Support range-based slicing for struct array data
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Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>
