[MFTF] Final set of changes to improve the MFTF tests

[lbajsarowicz]

Description (*)

This PR contains all other changes I introduced to MFTF and some more:

• Unified stepKey to be camelCase (lower first)
• Added ActionGroup suffix to all Action Groups
• Updated documentation to follow best practices

Fixed Issues (if relevant)

1. [ MFTF ] Mess in ActionGroups: invalid names, multiple nodes. magento2#26331

Manual testing scenarios (*)

Run MFTF tests for:

• https://github.com/magento/magento2
• https://github.com/magento/partners-magento2b2b
• https://github.com/magento/partners-magento2ee
• https://github.com/magento/magento2-page-builder
• https://github.com/magento/magento2-page-builder-ee

Related Pull Requests

• [MFTF] Final set of changes to improve the MFTF tests magento2#26570
• https://github.com/magento/partners-magento2b2b/pull/44
• https://github.com/magento/partners-magento2ee/pull/133
• [MFTF] Final set of changes to improve the MFTF tests magento2-page-builder#369
• https://github.com/magento/magento2-page-builder-ee/pull/104
• [MFTF] Final set of changes to improve the MFTF tests #563

Questions or comments

N/A

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 are green)

[lbajsarowicz]

@magento run Travis CI - Pull Request

[lbajsarowicz]

@magento run all tests

[lbajsarowicz]

We won't be able to do it in one PR.
Before things get merged, we have hundreds of conflicts :(