Fix #7686: Voice search not detecting sound

[soner-yuksel]

Checking availability of speech recognizer and device recognizer in order to display voice search icon

Summary of Changes

This pull request fixes #7686

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:

• Once on new tab, select the microphone icon in the URL bar
• Enable mic permissions for Brave
• Once the voice search modal opens, search query with your voice

And if the region of the user is not allowing voice search the button should be totally hidden

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).