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>

cmd/mattermost/main.go

@@ -6,18 +6,6 @@ package main
 import (
 	"os"
 
-	// Enterprise Deps
-	_ "github.com/gorilla/handlers"
-	_ "github.com/hako/durafmt"
-	_ "github.com/hashicorp/memberlist"
-	_ "github.com/mattermost/gosaml2"
-	_ "github.com/mattermost/ldap"
-	_ "github.com/mattermost/rsc/qr"
-	_ "github.com/prometheus/client_golang/prometheus"
-	_ "github.com/prometheus/client_golang/prometheus/promhttp"
-	_ "github.com/tylerb/graceful"
-	_ "gopkg.in/olivere/elastic.v6"
-
 	"github.com/mattermost/mattermost-server/v6/cmd/mattermost/commands"
 	// Import and register app layer slash commands
 	_ "github.com/mattermost/mattermost-server/v6/app/slashcommands"

cmd/mattermost/main_test.go

@@ -9,7 +9,7 @@ import (
 
 // TestRunMain can be used to track code coverage in integration tests.
 // To run this:
-// go test -coverpkg="<>" -mod=vendor -ldflags '<>' -tags maincoverage -c ./cmd/mattermost/
+// go test -coverpkg="<>" -ldflags '<>' -tags maincoverage -c ./cmd/mattermost/
 // ./mattermost.test -test.run="^TestRunMain$" -test.coverprofile=coverage.out
 // And then run your integration tests.
 func TestRunMain(t *testing.T) {