[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

api4/websocket_norace_test.go

@@ -21,15 +21,15 @@ func TestWebSocket(t *testing.T) {
 	th := Setup(t).InitBasic()
 	defer th.TearDown()
 	WebSocketClient, err := th.CreateWebSocketClient()
-	require.Nil(t, err)
+	require.NoError(t, err)
 	defer WebSocketClient.Close()
 
 	time.Sleep(300 * time.Millisecond)
 
 	// Test closing and reconnecting
 	WebSocketClient.Close()
-	err = WebSocketClient.Connect()
-	require.Nil(t, err)
+	appErr := WebSocketClient.Connect()
+	require.Nil(t, appErr)
 
 	WebSocketClient.Listen()