[Issue] code refactor, php8.x adjustmentts, param types, etc

[m2-assistant]

This issue is automatically created based on existing pull request: #39868: code refactor, php8.x adjustmentts, param types, etc

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Description (*)

Just some type fixes + upgrade to php8.x
Needs to be tested and validated properly, as some method properties still do not match in core.

I've made this fix due to this code:

   $items = $this->optionManagement->getItems(
         Product::ENTITY,
         $attributeCode
   );

as it suppose to be an integer, but string has to be passed as the $1 parameter

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)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)