arrow

GH-37724: [MATLAB] Add `arrow.type.StructType` MATLAB class (#37749)



### Rationale for this change

In order to add a `arrow.array.StructArray` MATLAB class (https://github.com/apache/arrow/issues/37653), we first need to implement the `arrow.type.StructType` MATLAB class.

### What changes are included in this PR?

1. Added a new MATLAB class `arrow.type.StructType`
2. Added convenience constructor function `arrow.struct()`
3. Added `Struct` as a enumeration value to `arrow.type.ID`
4. Added `arrow.type.traits.StructTraits` MATLAB class. Some of its properties, such as `ArrayConstructor` and `ArrayProxyClassName`, are set to `missing` because they require `arrow.array.StructArray` (#37653). When that class is added, we can initialize these properties to correct values.

**Example Usage**
```matlab
>> fieldA = arrow.field("A", arrow.int32());
>> fieldB = arrow.field("B", arrow.timestamp(TimeZone="America/New_York"));
>> fieldC = arrow.field("C", arrow.string());
>> structType = arrow.struct(fieldA, fieldB, fieldC)

structType = 

  StructType with properties:

        ID: Struct
    Fields: [1×3 arrow.type.Field]

>> fieldBFromStruct = structType.field(2)

fieldBFromStruct = 

B: timestamp[us, tz=America/New_York]
```

### Are these changes tested?

Yes.

1. Added a new test class called `tStructType.m`
2. Added a new test case to `tTypeDisplay.m`
3. Updated test case in `tID.m`

### Are there any user-facing changes?

Yes. Users can now create an `arrow.type.StructType` object using the new `arrow.struct()` funciton.

### Future Directions

1. #37653
* Closes: #37724

Authored-by: Sarah Gilmore <sgilmore@mathworks.com>
Signed-off-by: Kevin Gurney <kgurney@mathworks.com>