Fix #6912: Add new search engines for South Korea region

[iccub]

Summary of Changes

This pull request fixes #6912

Submitter Checklist:

• Unit Tests are updated to cover new or changed functionality
• User-facing strings use NSLocalizableString()
• New or updated UI has been tested across:
  • Light & dark mode
  • Different size classes (iPhone, landscape, iPad)
  • Different dynamic type sizes

Test Plan:

Set your device region to South Korea.
Verify that Naver is set as default engine.
Verify that Daum search engine is available.
Verify that both search engines work and their search suggestions work as well
Verify that these search engines do not show for non South Korea region users

Screenshots:

Reviewer Checklist:

• Issues include necessary QA labels:
  • QA/(Yes|No)
  • bug / enhancement
• Necessary security reviews have taken place.
• Adequate unit test coverage exists to prevent regressions.
• Adequate test plan exists for QA to validate (if applicable).
• Issue and pull request is assigned to a milestone (should happen at merge time).

[simonhong]

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