refactor: replace misleading $quoteTransfer variable names with generic $abstractTransfer to reflect abstract transfer usage

[greinerdavid]

PR Description

AbstractTransfers are used in the spryker/step-engine package, which are a $quoteTransfer according to the annotation and variable name. This leads to misunderstandings and links the step engine to the checkout. However, as the step engine can also be used for other multi-step forms (wizards) independently of the checkout, it should not be linked to the checkout in the wording.

Steps before you submit a PR

• Please add tests for the code you add if it's possible.
• Please check out our contribution guide: https://docs.spryker.com/docs/dg/dev/code-contribution-guide.html
• Add a contribution-license-agreement.txt file with the following content:
  I hereby agree to Spryker\'s Contribution License Agreement in https://github.com/spryker/step-engine/blob/HASH_OF_COMMIT_YOU_ARE_BASING_YOUR_BRANCH_FROM_MASTER_BRANCH/CONTRIBUTING.md.

This is a mandatory step to make sure you are aware of the license agreement and agree to it. HASH_OF_COMMIT_YOU_ARE_BASING_YOUR_BRANCH_FROM_MASTER_BRANCH is a hash of the commit you are basing your branch from the master branch. You can take it from commits list of master branch before you submit a PR.

Checklist

• I agree with the Code Contribution License Agreement in CONTRIBUTING.md

[spryker-release-bot]

Dear contributor,

Your pull request will be reviewed by our team. In the meantime, please ensure that the PR complies with Spryker's coding guidelines and that your changes are covered by tests.

Thank you very much for your contribution to the development of Spryker and the growth of the Spryker community!

[matweew]

Released in https://github.com/spryker/step-engine/releases/tag/3.7.0. Could you please close the PR.

[greinerdavid]

@matweew thank you very much. I closed the pr now.