[MM-49989] Pass a context.Context to Client4 methods (#22922)

* Migrate all method in model/client4.go to accept a context.Context

* Fix th.*Client

* Fix remaining issues

* Empty commit to triger CI

* Fix test

* Add cancellation test

* Test that returned error is context.Canceled

* Fix bad merge

* Update mmctl code

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/api4/data_retention_test.go

@@ -4,6 +4,7 @@
 package api4
 
 import (
+	"context"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -13,7 +14,7 @@ func TestDataRetentionGetPolicy(t *testing.T) {
 	th := Setup(t)
 	defer th.TearDown()
 
-	_, resp, err := th.Client.GetDataRetentionPolicy()
+	_, resp, err := th.Client.GetDataRetentionPolicy(context.Background())
 	require.Error(t, err)
 	CheckNotImplementedStatus(t, resp)
 }