test: check contextify contextual store behavior in strict mode

Previously, this behavior was tested indirectly by the REPL tests.
However, REPL now uses DONT_CONTEXTIFY for its VM context.

Author: Renegade334

test/parallel/test-vm-global-contextual-store.js

@@ -0,0 +1,19 @@
+'use strict';
+
+require('../common');
+const assert = require('assert');
+const vm = require('vm');
+
+const ctx = vm.createContext({ x: 0 });
+
+// Global properties should be intercepted in strict mode
+vm.runInContext('"use strict"; x = 42', ctx);
+assert.strictEqual(ctx.x, 42);
+
+// Contextual store should only be intercepted in non-strict mode
+vm.runInContext('y = 42', ctx);
+assert.strictEqual(ctx.y, 42);
+
+assert.throws(() => vm.runInContext('"use strict"; z = 42', ctx),
+              /ReferenceError: z is not defined/);
+assert.strictEqual(Object.hasOwn(ctx, 'z'), false);