Remove raw keys from normalized items in Normalizer

[WarLikeLaux]

Q	A
Is bugfix?	❌
New feature?	❌
Docs added?	❌
Tests added?	✔️
Breaks BC?	❌

What does this PR do?

Normalizer::dropdown() and Normalizer::menu() extract icon, iconAttributes, iconClass, iconContainerAttributes via helper methods and pass them to renderLabel(). The label() helper also reads encode. After extraction, these keys stay in the normalized item array alongside the processed results (label, active, link, etc.).

This PR adds unset() for these five keys after they are consumed, so the normalized output only contains processed data.

Neither Dropdown nor Menu read these keys from normalized items, so removing them is safe.

No BC break: the normalized array is internal, not part of the public API.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (e57424b) to head (5645914).

Additional details and impacted files

@@             Coverage Diff             @@
##              master      #132   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
  Complexity       283       283           
===========================================
  Files              8         8           
  Lines            892       904   +12     
===========================================
+ Hits             892       904   +12     

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