Fix #7702: OpenSearch issues - [hackerone 2057565]

[soner-yuksel]

Summary of Changes

This pull request fixes #7702

This pull request handles multitude of problems and security concerns

• Prevent custom search engine be added more than once
• If Show Search Suggestions off, do not send request with Search Suggestions API
• Show both search template and suggestion template URL on the description alert
• Not let custom search engine be added if search template or suggestion template is not having secure URL

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:

• Visit https://en.m.wikipedia.org/wiki/Main_Page
• Click magnifier button and activate search
• Click add custom search engine button over keyboard
• Check both suggestion - search URL template is written on description on alert

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).

[stoletheminerals]

Thanks @soner-yuksel