Enable internal translate engine

[atuchin-m]

Resolves brave/brave-browser#18593
Core:

• A new base::Feature and a flag are added;
• Both buildflags are enabled for desktop platforms, the decision of how to work (using the translate extension or the internal engine) is based on a new feature in runtime;

UI:

• The original chromium translation bubble was restored, but the custom bubble (that suggests the extension installation) also works well.
• context menu available when a user doesn't use the translate extension or we don't suggest installing it.

Network and the translate script:

• C++ redirections for the script are replaced to js redirections. Thay way we can split them from the other requests.
• Modified CSP for the translate isolated world is used to limit requests to *.brave.com
• Translate urls in C++ code are changed to translate-relay.brave.com using chromium switches.
• Language list requests are disabled by default.
• the dummy translate fetcher and tests are removed, translate_script is patched by chromium_src instead.

Bowser tests for redirection will be added if anything is ok.

Submitter Checklist:

• I confirm that no security/privacy review is needed, or that I have requested one
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• 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)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• 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:

[atuchin-m]

@fmarier could you please take a look?
It's related to https://github.com/brave/security/issues/613
Moreover you could find the discussion about the other options in #machine-translation channel.

[fmarier]

Thanks @atuchin-m . I looked at the hostname replacement code and that looked fine to me.

[atuchin-m]

Thanks @atuchin-m . I looked at the hostname replacement code and that looked fine to me.

Thanks @fmarier.
Please take into account that it doesn't redirect all the requests (only useful for us). The rest (for example google telemetry) will be banned using CSP:

[atuchin-m]

@simonhong @yrliou @iefremov PTAL

[simonhong]

views: ++ (not familiar with other core translate part)