[MM-37557] Move error out of client4 response (#18101)

* Return an error seperately from Response

* Remove BuildErrorResponse

* Drop Response.Error from model/client4.go

* Migrate require.Nil checks

* Migrate require.NotNil checks

* More manual fixes

* Move error check out of CheckOKStatus and CheckCreatedStatus

* Move error check out of CheckForbiddenStatus

* Move error check out of CheckUnauthorizedStatus

* Move error check out of CheckNotFoundStatus

* Move error check out of CheckBadRequestStatus

* Move error check out of CheckNotImplementedStatus and CheckRequestEntityTooLargeStatus

* Move error check out of CheckInternalErrorStatus

* Move error check out of CheckServiceUnavailableStatus

* Remove error check from checkHTTPStatus

* Remove remaining references to Response.Error

* Check previously unchecked errors

* Manually fix compile and linter errors

* Return error in CreateWebSocket methods

* Return error instead of *AppError in DoApi methods

* Manually fix bad replacments

* Conistently return Response and error

* Use err instead of seperate bool return value to indicate success

* Reduce ussage of model.AppError in web/oauth_test.go

* Remove client4.Must

* Check error in buf.ReadFrom

* Fix failing tests

model/websocket_client_test.go

@@ -46,7 +46,7 @@ func TestWebSocketRace(t *testing.T) {
 
 	url := strings.Replace(s.URL, "http://", "ws://", 1)
 	cli, err := NewWebSocketClient4(url, "authToken")
-	require.Nil(t, err)
+	require.NoError(t, err)
 
 	cli.Listen()
 
@@ -110,7 +110,7 @@ func TestWebSocketClose(t *testing.T) {
 
 	t.Run("SuddenClose", func(t *testing.T) {
 		cli, err := NewWebSocketClient4(url, "authToken")
-		require.Nil(t, err)
+		require.NoError(t, err)
 
 		cli.Listen()
 
@@ -132,7 +132,7 @@ func TestWebSocketClose(t *testing.T) {
 
 	t.Run("ExplicitClose", func(t *testing.T) {
 		cli, err := NewWebSocketClient4(url, "authToken")
-		require.Nil(t, err)
+		require.NoError(t, err)
 
 		cli.Listen()