Fix: Remove custom parameters in topic settings/creation form

[RotemCDos]

• Breaking change? (if so, please describe the impact and migration path for existing application instances)

What changes did you make? (Give an overview)

Previously, the removeField function in the parent component (CustomParams.tsx) was relying on the index which could be stale.

1. Moved the removal logic inside the CustomParamField component. Now, each field is responsible for removing itself from the existingFields list and then triggering the form removal.
2. Moved the remove(index) call outside the if (itemIndex !== -1) check which was the root cause for the skip (if the custom param name was empty).

Is there anything you'd like reviewers to focus on?

How Has This Been Tested? (put an "x" (case-sensitive!) next to an item)

• No need to
• Manually (please, describe, if necessary)
• Unit checks
• Integration checks
• Covered by existing automation

Checklist (put an "x" (case-sensitive!) next to all the items, otherwise the build will fail)

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (e.g. ENVIRONMENT VARIABLES)
• My changes generate no new warnings (e.g. Sonar is happy)
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged

Check out Contributing and Code of Conduct

This solves issue #1673

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