chore(cli): stops tests from interfering with each other (#32319)

Turn on test randomization: this causes tests to run in a random order, which will expose tests that only succeed because tests before them have left the system in a specific state (or that poison tests after them because they don't clean up).

Of course, doing this exposed that we have a number of such tests, clean those up as well.

This needed to clean up mocking a lot in the garbage collector code, because it was confusing. Also remove the side-effect mock resetting that happens whenver a `MockSdk()` is instantiated, since that caused prepared mock behavior to be cleared.

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: rix0rrr

packages/aws-cdk/jest.config.js

@@ -1,5 +1,6 @@
 const baseConfig = require('@aws-cdk/cdk-build-tools/config/jest.config');
-module.exports = {
+
+const config = {
     ...baseConfig,
     coverageThreshold: {
         global: {
@@ -21,4 +22,18 @@ module.exports = {
     // We have many tests here that commonly time out
     testTimeout: 30_000,
     setupFilesAfterEnv: ["<rootDir>/test/jest-setup-after-env.ts"],
+
+    // Randomize test order: this will catch tests that accidentally pass or
+    // fail because they rely on shared mutable state left by other tests
+    // (files on disk, global mocks, etc).
+    randomize: true,
 };
+
+// Disable coverage running in the VSCode debug terminal: we never want coverage
+// when we're attaching a debugger because the coverage injection messes with
+// the source maps.
+if (process.env.VSCODE_INJECTION) {
+    config.collectCoverage = false;
+}
+
+module.exports = config;