[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/cmd/mmctl/commands/init_test.go

@@ -4,6 +4,7 @@
 package commands
 
 import (
+	"context"
 	"crypto/x509"
 	"encoding/json"
 	"net"
@@ -189,7 +190,7 @@ func TestNewAPIv4Client(t *testing.T) {
 		defer os.Unsetenv("HTTP_PROXY")
 
 		client := NewAPIv4Client("http://somethingelse:"+port, false, false)
-		_, _, err = client.GetMe("")
+		_, _, err = client.GetMe(context.Background(), "")
 		require.NoError(t, err)
 	})
 }