chore: add lint rule to prevent .only usage (#3085)

Author: nbbeeken

.eslintrc.json

@@ -23,6 +23,21 @@
     "es6": true
   },
   "rules": {
+    "no-restricted-properties": [
+      "error",
+      {
+        "object": "describe",
+        "property": "only"
+      },
+      {
+        "object": "it",
+        "property": "only"
+      },
+      {
+        "object": "context",
+        "property": "only"
+      }
+    ],
     "prettier/prettier": "error",
     "tsdoc/syntax": "warn",
     "no-console": "error",

test/functional/change_stream_spec.test.js

@@ -83,7 +83,10 @@ describe('Change Stream Spec - v1', function () {
 
       suite.tests.forEach(test => {
         const shouldSkip = test.skip || TESTS_TO_SKIP.has(test.description);
-        const itFn = shouldSkip ? it.skip : test.only ? it.only : it;
+        // There's no evidence of test.only being defined in the spec files
+        // But let's avoid removing it now to just be sure we aren't changing anything
+        // These tests will eventually be replaced by unified format versions.
+        const itFn = shouldSkip ? it.skip : test.only ? Reflect.get(it, 'only') : it;
         const metadata = generateMetadata(test);
         const testFn = generateTestFn(test);