Fix a bug where pages can disable translation via html tags and the o…

[Brandon-T]

Summary

• Detect when the translation for a page isn't fully loaded yet, such as on Google where the page loads entirely in Javascript first, then that Javascript dynamically loads the HTML
• Fix translation Onboarding showing up on a page where it's not supported (Cannot translate English to English).
• Fix translation Onboarding crash when tapping the icon in the URL-Bar

Resolves brave/brave-browser#44272

Submitter Checklist:

• I confirm that no security/privacy review is needed and no other type of reviews are needed, or that I have requested them
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• 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 wiki
  • npm run presubmit wiki, 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/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

[Brandon-T]

This makes sure we don't translate from en to en for example. So a page cannot be translated if it's already in your desired language.

[Brandon-T]

This fixes the CheckedContinuation crash. dismissPopover already calls the completion

[Brandon-T]

This fixes the Onboarding button sometimes showing as if it's blended with reader-mode or in the wrong spot. It's because the page isn't ready to be translated yet, so onboarding showed up early.

The timeout didn't help, so it's removed in favour of just checking if the script is ready.

[brave-builds]

Released in v1.78.4

[hffvld]

Verified on iPhone 14 and iPad Mini (6th gen) using version(s):

Device/OS: 
- iPhone 14 / iOS 17.7.2
- iPad Mini (6th gen) / iPadOS 18.3
Brave build: 1.78 (6)
BraveCore: 1.78.6 (134.0.6998.39)

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Translate Onboarding pop-up

STEPS:

1. Fresh Install Brave
2. Open a brand new tab
3. Tap on the URL Bar
4. Type: Wiki
5. Tap on the Google icon in the quick-search to search with the Google search engine > Verify

ACTUAL RESULTS:

• Verified that the Translate onboarding pop-up is not shown on the incorrect page.

---

Reproduced with 1.77(70)

iPhone 14	iPad Mini

Verified with 1.78 (6)

iPhone 14	iPad Mini
Screencast	Screencast

Brave crash

STEPS:

1. Fresh Install Brave
2. Open a brand new tab
3. Tap on Wikipedia thumbnail
4. Tap on Russian, Japanese, Spanish or another language that is NOT the same as the system language
5. Translate Onboarding pop-up shows
6. Tap on the highlighted icon in the URL Search Bar > Verify

ACTUAL RESULTS:

• Verified that Brave doesn't crash if tapping Translate Onboarding pop-up.

---

iPhone 14	iPad Mini
Screencast	Screencast