apacheGH-37251: [MATLAB] Make arrow.type.TemporalType a "tag" class (…

…apache#37256)

### Rationale for this change

The original motivation for adding the super-class `arrow.type.TemporalType` in apache#37236 was to define a common implementation for extracting the `Unit` property from `TimestampType`, `Time32Type`, `Time64Type`, `Date32Type`, and `Date64Type`. However, this approach doesn't work because the `Unit` property on `Date32Type` and `Date64Type` is a `DateUnit`, while the `Unit` property on the other three types is a`TimeUnit`. As a result, we cannot define a shared method for extracting the `Unit` property in `TemporalType`. 

Instead, we plan on making `arrow.type.TemporalType` a "tag"-class (i.e. it has no properties or methods) so it can be used to group the "temporal" types together to ease authoring conditional logical in client code. In a future PR, we plan on adding functions like `arrow.type.isTemporal`, `arrow.type.isNumeric`, etc. so that clients don't need to query the class type information directly (i.e. call `isa(type, "arrow.type.TemporalType")`). 

```matlab
function doStuff(arrowArray)
  import arrow.*

  arrowType = arrowArray.Type;
  if type.isTemporal(arrowType)
      ...
  else if type.isNumeric(arrowType)
      ...
  else 
      ...
  end
end
```

### What changes are included in this PR?

1. Removed the `TimeUnit` property from `arrow.type.TemporalType`
2. Added `TimeUnit` back as a property on `arrow.type.TimestampType` and `arrow.type.Time32Type`

### Are these changes tested?

Yes, the existing tests cover these changes.

### Are there any user-facing changes?

No.

### Future Directions
1. apache#37232
2. apache#37229
3. apache#37230

* Closes: apache#37251

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

matlab/src/matlab/+arrow/+type/TemporalType.m

@@ -17,21 +17,12 @@
 
 classdef TemporalType < arrow.type.FixedWidthType
 
-    properties(Dependent, GetAccess=public, SetAccess=private)
-        TimeUnit
-    end
-
     methods
         function obj = TemporalType(proxy)
             arguments
                 proxy(1, 1) libmexclass.proxy.Proxy
             end
             obj@arrow.type.FixedWidthType(proxy);
         end
-
-        function timeUnit = get.TimeUnit(obj)
-            timeUnitValue = obj.Proxy.getTimeUnit();
-            timeUnit = arrow.type.TimeUnit(timeUnitValue);
-        end
     end
 end

matlab/src/matlab/+arrow/+type/Time32Type.m

@@ -17,6 +17,10 @@
 
 classdef Time32Type < arrow.type.TemporalType
 
+    properties(Dependent, GetAccess=public, SetAccess=private)
+        TimeUnit
+    end
+
     methods
         function obj = Time32Type(proxy)
             arguments
@@ -26,6 +30,11 @@
 
             obj@arrow.type.TemporalType(proxy);
         end
+
+        function timeUnit = get.TimeUnit(obj)
+            timeUnitValue = obj.Proxy.getTimeUnit();
+            timeUnit = arrow.type.TimeUnit(timeUnitValue);
+        end
     end
 
     methods (Access=protected)

matlab/src/matlab/+arrow/+type/TimestampType.m

@@ -1,3 +1,5 @@
+%TIMESTAMPTYPE Type class for timestamp data.
+
 % Licensed to the Apache Software Foundation (ASF) under one or more
 % contributor license agreements.  See the NOTICE file distributed with
 % this work for additional information regarding copyright ownership.
@@ -14,9 +16,9 @@
 % permissions and limitations under the License.
 
 classdef TimestampType < arrow.type.TemporalType
-%TIMESTAMPTYPE Type class for timestamp data.
 
     properties(Dependent, GetAccess=public, SetAccess=private)
+        TimeUnit
         TimeZone
     end
 
@@ -29,6 +31,11 @@
             obj@arrow.type.TemporalType(proxy);
         end
 
+        function timeUnit = get.TimeUnit(obj)
+            timeUnitValue = obj.Proxy.getTimeUnit();
+            timeUnit = arrow.type.TimeUnit(timeUnitValue);
+        end
+
         function tz = get.TimeZone(obj)
             tz = obj.Proxy.getTimeZone();
         end