[RHELC-1687] - conftest.py refactor - custom repos

[kokesak]

Refactor how we use the custom repositories in conftest.py.

Jira Issues:

• RHELC-1687
• RHELC-1620

Checklist

• [ ] PR has been tested manually in a VM (either author or reviewer)
• [ ] Jira issue has been made public if possible
• [ ] [RHELC-] or [HMS-] is part of the PR title
• [ ] GitHub label has been added to help with Release notes
• [ ] PR title explains the change from the user's point of view
• [ ] Code and tests are documented properly
• [ ] The commits are squashed to as few commits as possible (without losing data)
• [ ] When merged: Jira issue has been updated to Release Pending if relevant

[has-bot]

This PR does not require integration tests to be run.

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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.34%. Comparing base (841cf50) to head (570a8b8). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1370 +/- ## ======================================= Coverage 96.34% 96.34% ======================================= Files 66 66 Lines 4983 4983 Branches 877 877 ======================================= Hits 4801 4801 Misses 102 102 Partials 80 80 ``` | [Flag](https://app.codecov.io/gh/oamg/convert2rhel/pull/1370/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=oamg) | Coverage Δ | | |---|---|---| | [centos-linux-7](https://app.codecov.io/gh/oamg/convert2rhel/pull/1370/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=oamg) | `91.76% <ø> (ø)` | | | [centos-linux-8](https://app.codecov.io/gh/oamg/convert2rhel/pull/1370/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=oamg) | `92.64% <ø> (ø)` | | | [centos-linux-9](https://app.codecov.io/gh/oamg/convert2rhel/pull/1370/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=oamg) | `92.69% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=oamg#carryforward-flags-in-the-pull-request-comment) to find out more.

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[has-bot]

/packit test --labels tier0

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[kokesak]

/packit test --labels tier0

[kokesak]

/packit build

[kokesak]

/packit test --labels tier0

[kokesak]

/packit test --labels tier0

[kokesak]

/packit test --labels tier0