Update test framework: fix run_tests.py to support all test files, add auto-import-check for test files

node_modules/import-in-the-middle/test/fixtures/package.json

@@ -0,0 +1,17 @@
+{
+    "name": "test-fixtures",
+    "imports": {
+      "#main-entry-point": {
+        "require": {
+          "node": "./something.js",
+          "default": "./something.js"
+        },
+        "import": {
+          "node":"./something.mjs",
+          "default": "./something.mjs"
+        }
+      },
+      "#main-entry-point-string" : "./something.js",
+      "#main-entry-point-external" : "some-external-cjs-module"
+    }
+}