GH-37245: [MATLAB] arrow.internal.proxy.validate throws `MATLAB:Und…

…efinedFunction` when crafting the message to display when throwing the `arrow:proxy:ProxyNameMismatch` error (#37248)

### Rationale for this change

When constructing the message to display for with the `arrow:proxy:ProxyNameMismatch` error,  we refer to an undefined variable in `arrow.internal.proxy.validate()`. This causes the function to throw a `MATLAB:UndefinedFunction` error instead of the intended one.

Here's an example of this bug:

```matlab
>> a = arrow.array([1 2 3]);
>> arrow.internal.proxy.validate(a.Proxy, "WrongProxyName")
Unrecognized function or variable 'proxyName'.

Error in arrow.internal.proxy.validate (line 26)
        msg = "Proxy class name is " + proxyName + ", but expected " + expectedProxyName;
```

This was the expected error message:

```matlab
>> a = arrow.array([1 2 3]);
>> arrow.internal.proxy.validate(a.Proxy, "WrongProxyName")
Error using arrow.internal.proxy.validate
Proxy class name is arrow.array.proxy.Float64Array, but expected WrongProxyName
```

### What changes are included in this PR?

1. Fixed the typos in `arrow.internal.proxy.validate()` to resolve the `MATLAB:UndefinedFunction` error
2. Added a new test class `test/arrow/internal/proxy/tValidate.m` to test  `arrow.internal.proxy.validate()`
3. Updated the error message to display when throwing an `arrow:proxy:ProxyNameMismatch` error: 

```matlab
>> a = arrow.array([1 2 3]);
>> arrow.internal.proxy.validate(a.Proxy, "WrongProxyName")
Error using arrow.internal.proxy.validate
The Name property of the Proxy provided is "arrow.array.proxy.Float64Array", but
expected it to be "WrongProxyName".
```

### Are these changes tested?

Yes, added a new test class `test/arrow/internal/proxy/tValidate.m`.

### Are there any user-facing changes?

No.

* Closes: #37245

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

matlab/src/matlab/+arrow/+internal/+proxy/validate.m

@@ -18,12 +18,13 @@ function validate(proxy, expectedName)
 % proxy.Name and expectedName are not equal.
     arguments
         proxy(1, 1) libmexclass.proxy.Proxy
-        expectedName(1, 1) string
+        expectedName(1, 1) string {mustBeNonmissing, mustBeNonzeroLengthText}
     end
 
     if proxy.Name ~= expectedName
         errid = "arrow:proxy:ProxyNameMismatch";
-        msg = "Proxy class name is " + proxyName + ", but expected " + expectedProxyName;
+        msg = compose("The Name property of the Proxy provided is ""%s"", " + ...
+            "but expected it to be ""%s"".", proxy.Name, expectedName);
         error(errid, msg);
     end
 end

matlab/test/arrow/internal/proxy/tValidate.m

@@ -0,0 +1,42 @@
+%TVALIDATE Unit tests for arrow.internal.proxy.validate
+
+% 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.
+% The ASF licenses this file to you under the Apache License, Version
+% 2.0 (the "License"); you may not use this file except in compliance
+% with the License.  You may obtain a copy of the License at
+%
+%   http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, software
+% distributed under the License is distributed on an "AS IS" BASIS,
+% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+% implied.  See the License for the specific language governing
+% permissions and limitations under the License.
+
+classdef tValidate < matlab.unittest.TestCase
+
+    methods(Test)
+        function ProxyNameMatches(testCase)
+            % Verify arrow.internal.proxy.validate() does not throw an 
+            % error if the Name property of the Proxy provided matches
+            % the expected proxy name.
+            import arrow.internal.proxy.validate
+            a = arrow.array(1);
+            fcn = @() validate(a.Proxy, a.Proxy.Name);
+            testCase.verifyWarningFree(fcn);
+        end
+
+        function ProxyNameMismatchError(testCase)
+            % Verify arrow.internal.proxy.validate() throws an error 
+            % whose identifier is "arrow:proxy:ProxyNameMismatch" if the
+            % Name property of the Proxy provided does not match the 
+            % expected proxy name.
+            import arrow.internal.proxy.validate
+            a = arrow.array(1);
+            fcn = @() validate(a.Proxy, "NotAProxyName");
+            testCase.verifyError(fcn, "arrow:proxy:ProxyNameMismatch");
+        end
+    end
+end