chore: Internal portal util

[pan-kot]

Moves portal from https://github.com/cloudscape-design/components/tree/main/src/internal/components/portal to toolkit, to be reused in chart components.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.33%. Comparing base (b062d4f) to head (53597b4).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #129      +/-   ##
==========================================
+ Coverage   99.30%   99.33%   +0.03%     
==========================================
  Files          29       30       +1     
  Lines         717      751      +34     
  Branches      192      199       +7     
==========================================
+ Hits          712      746      +34     
  Misses          5        5              

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