test: check inspector support in test/inspector

When configuring node --without-ssl or --without-inspector these test
will fail. The underlying issue will be:

Inspector support is not available with this Node.js build
/work/nodejs/node/out/Release/node: bad option: --inspect=0

This commit adds checks to see if inspector support is enabled and if
not skips these tests.

PR-URL: #13324
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@chromium.org>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: danbev

test/inspector/test-inspector-port-zero-cluster.js

@@ -2,6 +2,7 @@
 'use strict';
 
 const common = require('../common');
+common.skipIfInspectorDisabled();
 const assert = require('assert');
 const cluster = require('cluster');
 

test/inspector/test-inspector-port-zero.js

@@ -1,6 +1,7 @@
 'use strict';
 
-const { mustCall } = require('../common');
+const { mustCall, skipIfInspectorDisabled } = require('../common');
+skipIfInspectorDisabled();
 const assert = require('assert');
 const { URL } = require('url');
 const { spawn } = require('child_process');