Set Yandex as default

[deeppandya]

Resolves brave/brave-browser#12979

Submitter Checklist:

• There is a ticket for my issue.
• Used Github auto-closing keywords in the commit message.
• Wrote a good PR/commit description
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally: npm run test -- brave_browser_tests, npm run test -- brave_unit_tests, npm run lint, npm run gn_check, npm run tslint
• Ran git rebase master (if needed).
• Requested a security/privacy review as needed.

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on.
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

Please follow main issue for test plan

[SergeyZhukovsky]

I don't think we need that log anymore

[SergeyZhukovsky]

++

[kjozwiak]

Verification PASSED on Pixel 2 XL running Android 11 using the following build:

Brave | 1.20.19 Chromium: 87.0.4280.101 (Official Build) canary (32-bit)
--- | ---
Revision | 9407c80213cda69c2b7abcb4fa8e3f74488f4956-refs/branch-heads/4280@{#1807}
OS | Android 11; Pixel 2 XL Build/RP1A.201005.004

• ensured that Yandex was selected as the default search engine for the following locales:
  • Russia, Armenia, Belarus & Kyrgyz Republic
• ensured that updating from 1.20.17 CR: 87.0.4280.88 --> 1.20.19 Chromium: 87.0.4280.101 didn't replace the previous default SE with Yandex

Note: Some of these regions don't have any localization but I ensured that:

• Yandex is being set as the default
• Yandex is available via the SE onboarding

Russia Examples

Example 1	Example 2

Armenia Examples

Example 1	Example 2