MM-43753: Module workspaces (#20113)

* MM-43753: Module workspaces

Move to module workspaces

We make the following changes:
- Remove the vendor directory.
- Dynamically create the go.work file if it doesn't exist.
- Set the MM_SERVER_PATH for enterprise tests.

https://mattermost.atlassian.net/browse/MM-43753

```release-note
NONE
```

* Fix missing reference to MM_SERVER_PATH

```release-note
NONE
```

* Update test to add another nested dir

```release-note
NONE
```

* Have separate script to create go.work file

```release-note
NONE
```

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

.gitignore

@@ -25,6 +25,10 @@ config/logging.json
 # Enterprise imports file
 imports/imports.go
 
+# go.work file
+go.work
+go.work.sum
+
 #license files
 *.license
 *.mattermost-license