Add tests against multiple MongoDB versions (#7161)

* added tests environment with mongodb 4.4.3

* added CI test for mongodb 4.4.3

* added CI tests for MongoDB versions 4.0, 4.2

* improved flaky test (seems to max out the limit of simultaneous connections)

* added spec helpers to run tests only for specific MongoDB version

* addedn npm scripts to run tests against relevant mongodb versions

* added spec helper function to exclude specific mongodb version

* added test for changed aggregate query planner results

* fixed regex test with incorrect regex syntax

* fixed test where query has select no keys (empty array)

* added changelog entry and ordered list

* fixed test that tried to simultaneously delete and build index on same collection

* added MongoDB compatibility table to readme

* updated default local tests to use MongoDB 4.4.3

* added MongoDB badges for new versions to README

* fixed typo in readme

* added new test helper filter to contribution guide

* fixed incorrect storage engine for mongodb 4.4

* changed CI to test MongoDB 3.6. with mmapv1 storage engine and standalone

* improved CI test description

* added CI self check for new MongoDB versions

* fixed CI

* removed CI

* added CI

* added throwing error if any of the checks failed

* added github action connector

* improved error message

* improved error messages

* improved error message

* updated CI environment to MongoDB 3.6.22

* improved error messages

* update CI env name

* updated CI env name

* improved error message

* removed patch versions from CI env description

* improved status message

* removed version range from core lib

* added explicit mongodb version to redis test and node 12 test

* bumped Node 12 test to 12.20.1 (version currently recommended by AWS Elastic Beanstalk)

spec/helper.js

@@ -1,4 +1,6 @@
 'use strict';
+const semver = require('semver');
+
 // Sets up a Parse API server for testing.
 jasmine.DEFAULT_TIMEOUT_INTERVAL = process.env.PARSE_SERVER_TEST_TIMEOUT || 5000;
 
@@ -417,6 +419,42 @@ global.it_only_db = db => {
   }
 };
 
+global.it_only_mongodb_version = version => {
+  const envVersion = process.env.MONGODB_VERSION;
+  if (!envVersion || semver.satisfies(envVersion, version)) {
+    return it;
+  } else {
+    return xit;
+  }
+};
+
+global.fit_only_mongodb_version = version => {
+  const envVersion = process.env.MONGODB_VERSION;
+  if (!envVersion || semver.satisfies(envVersion, version)) {
+    return fit;
+  } else {
+    return xit;
+  }
+};
+
+global.it_exclude_mongodb_version = version => {
+  const envVersion = process.env.MONGODB_VERSION;
+  if (!envVersion || !semver.satisfies(envVersion, version)) {
+    return it;
+  } else {
+    return xit;
+  }
+};
+
+global.fit_exclude_mongodb_version = version => {
+  const envVersion = process.env.MONGODB_VERSION;
+  if (!envVersion || !semver.satisfies(envVersion, version)) {
+    return fit;
+  } else {
+    return xit;
+  }
+};
+
 global.fit_exclude_dbs = excluded => {
   if (excluded.indexOf(process.env.PARSE_SERVER_TEST_DB) >= 0) {
     return xit;