More transformer v2 refactoring

[major]

This brings the other transformers in line with yesterday's update and also extracts the entry filtering to its own method.

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.50% :tada:

Comparison is base (aade645) 93.10% compared to head (f9c0540) 93.60%.

:exclamation: Current head f9c0540 differs from pull request most recent head 913dae2. Consider uploading reports for the commit 913dae2 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #696 +/- ## ========================================== + Coverage 93.10% 93.60% +0.50% ========================================== Files 9 9 Lines 551 532 -19 Branches 116 110 -6 ========================================== - Hits 513 498 -15 + Misses 20 18 -2 + Partials 18 16 -2 ``` | [Files Changed](https://app.codecov.io/gh/redhatcloudx/transformer/pull/696?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=redhatcloudx) | Coverage Δ | | |---|---|---| | [src/cloudimagedirectory/transform/transform.py](https://app.codecov.io/gh/redhatcloudx/transformer/pull/696?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=redhatcloudx#diff-c3JjL2Nsb3VkaW1hZ2VkaXJlY3RvcnkvdHJhbnNmb3JtL3RyYW5zZm9ybS5weQ==) | `91.77% <100.00%> (+0.72%)` | :arrow_up: |

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[F-X64]

LGTM but I'll leave the final judgement to @miyunari ;) Deployed the branch on staging for testing and it seems to run as expected: https://github.com/redhatcloudx/transformer/actions/runs/5723343231/job/15507786157