#19835 Fix admin header buttons flicker

[Bravarg]

Description (*)

Fixed button flicker issue after page load due to re-ordering.
It happens because "floatingHeader" widget, that wraps header buttons in flex container. However during page loading buttons aren't in flexbox wrapper.

Fixed Issues (if relevant)

1. Admin grid button flicker issue after page load due to re-ordering #19835: Admin grid button flicker issue after page load due to re-ordering

Manual testing scenarios (*)

1. Open any admin page with more than 1 button in header. For example: Content -> Design -> Configuration and open design configuration of any scope. During page rendering buttons in header are change their order and can be misclicked to wrong button.

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-cicd2]

All committers have signed the CLA.

[magento-engcom-team]

Hi @OlehWolf. Thank you for your contribution
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[sivaschenko]

@OlehWolf thanks for the pull request! We will be able to process it once you sing the CLA

[dmytro-ch]

@magento-engcom-team give me test instance

[magento-engcom-team]

Hi @dmytro-ch. Thank you for your request. I'm working on Magento instance for you

[magento-engcom-team]

Hi @dmytro-ch, here is your new Magento instance.
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[dmytro-ch]

Hi @OlehWolf,
thank you for your contribution!

Could you please check the code review comment?

Thank you!

[magento-engcom-team]

Hi @dmytro-ch, thank you for the review.
ENGCOM-4522 has been created to process this Pull Request

[soleksii]

✔️ QA Passed

Result:

[ghost]

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