arrow

GH-38415: [MATLAB] Add indexing "slice" method to C++ Array Proxy class (#38674)



### Rationale for this change

In order to support MATLAB indexing semantics on the `arrow.array.Array` classes, we first need to add a method for "slicing" an Arrow Array to the C++ Array Proxy classes.

### What changes are included in this PR?

1. Added a `slice` method to the C++ Arrow Array Proxy class. 
2. Added a `slice` method to `arrow.array.Array`. This method invokes the `slice` method on the proxy class. 

**Example**

```matlab

>> a = arrow.array([1 2 NaN 4 5 NaN 7])

a = 

  Float64Array with 7 elements and 2 null values:

    1 | 2 | null | 4 | 5 | null | 7

% Note: MATLAB uses 1-based indexing.
>> slice = a.slice(int64(2), int64(4))

slice = 

  Float64Array with 4 elements and 1 null value:

    2 | null | 4 | 5

```

### Are these changes tested?

Yes, added a new test file called `tSlice.m`.

### Are there any user-facing changes?

The `slice` method is public, but [hidden](https://www.mathworks.com/help/matlab/matlab_oop/method-attributes.html). 

* Closes: #38415

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