chore(feature-tracker): simplifies struct handling

[bartoszmajsak]

Description

Refactors FeatureTracker-related functions to plain functions instead of Feature receivers. This eliminates unnecessary coupling with the Feature struct.

How Has This Been Tested?

make + manual with simple KServe setup (which I hope can be part of an automated test suite one day...)

Screenshot or short clip

Merge criteria

• [x] You have read the contributors guide.
• [x] Commit messages are meaningful - have a clear and concise summary and detailed explanation of what was changed and why.
• [x] Pull Request contains a description of the solution, a link to the JIRA issue, and to any dependent or related Pull Request.
• [x] Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• [x] The developer has manually tested the changes and verified that the changes work

[openshift-ci[bot]]

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This pull-request has been approved by: zdtsw

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