[EC-497] Fix memory leaks in tests (#3421)

* Add isolatedModules:true

* Add manual typechecking in CI for libs/ tests

libs/shared/jest.config.base.js

@@ -10,10 +10,15 @@ module.exports = {
   // Also anecdotally improves performance when run locally
   maxWorkers: 3,
 
-  // Jest does not use tsconfig.spec.json by default
   globals: {
     "ts-jest": {
+      // Jest does not use tsconfig.spec.json by default
       tsconfig: "<rootDir>/tsconfig.spec.json",
+      // Further workaround for memory leak, recommended here:
+      // https://github.com/kulshekhar/ts-jest/issues/1967#issuecomment-697494014
+      // Makes tests run faster and reduces size/rate of leak, but loses typechecking on test code
+      // See https://bitwarden.atlassian.net/browse/EC-497 for more info
+      isolatedModules: true,
     },
   },
 };