refactor: lift is4_2 method to global

Author: andymina

test/integration/change-streams/change_stream.test.ts

@@ -41,6 +41,9 @@ const initIteratorMode = async (cs: ChangeStream) => {
   return;
 };
 
+const is4_2Server = (serverVersion: string) =>
+  gte(serverVersion, '4.2.0') && lt(serverVersion, '4.3.0');
+
 // Define the pipeline processing changes
 const pipeline = [
   { $addFields: { addedField: 'This is a field added using $addFields' } },
@@ -54,9 +57,6 @@ describe('Change Streams', function () {
   let changeStream: ChangeStream;
   let db: Db;
 
-  const is4_2Server = (serverVersion: string) =>
-    gte(serverVersion, '4.2.0') && lt(serverVersion, '4.3.0');
-
   beforeEach(async function () {
     const configuration = this.configuration;
     client = configuration.newClient();
@@ -1791,9 +1791,6 @@ describe('ChangeStream resumability', function () {
     { error: 'CursorNotFound', code: 43, message: 'cursor not found' }
   ];
 
-  const is4_2Server = (serverVersion: string) =>
-    gte(serverVersion, '4.2.0') && lt(serverVersion, '4.3.0');
-
   beforeEach(function () {
     assert(this.currentTest != null);
     if (