[Forwardport][Fix #16655] Block totalbar not used in invoice create and credit memo create screens

[dverkade]

Original PR

#16656

Description

Upon investigation there is a totalbar block in the create invoice and credit memo screens which is not being used. This PR addresses that:

• Removed the unused Totalbar block from the invoice create and credit memo create layouts.
• Deprecated Totalbar class
• Deprecated totalbar template file

Fixed Issues

1. Block totalbar not used in invoice create and credit memo create screens #16655: Block totalbar not used in invoice create and credit memo create screens
2. Not possible to create an invoice in Magento 2.3 #16653: Not possible to create an invoice in Magento 2.3

Related PR's

There is a PR related to this PR, which does not solve the issue correctly.

1. $block->getTotals() is not countable #16563: $block->getTotals() is not countable

Manual testing scenarios

1. Create a new order
2. Create an invoice, screen will look the same as before the changes.
3. Update invoice quantity, screen will look the same as before the changes.
4. Create a credit memo, screen will look the same as before the changes.
5. Update credit memo quantity, screen will look the same as before the changes.

[magento-engcom-team]

Hi @dverkade. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

• @magento-engcom-team give me test instance - deploy test instance based on PR changes
• @magento-engcom-team give me {$VERSION} instance - deploy vanilla Magento instance

For more details, please, review the Magento Contributor Assistant documentation

[magento-engcom-team]

Hi @dverkade. Thank you for your contribution.
We will aim to release these changes as part of 2.3.0.
Please check the release notes for final confirmation.