fix(wallet): implement DApps decrypt screen

[Pavneet-Sing]

Resolves brave/brave-browser#23260

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
• 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, 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:

Enable "Desktop site" check from the menu

Same as desktop flow from PR 12386

1. Go to https://inb0x.life/ and click Connect
2. Unlock and Connect your wallet
3. Click Activate and Sign the message prompt
4. Click Generate Secured inb0x Key and then click Provide in the Public Encryption Key panel.
5. Click Send New Message and then send a test message to another Wallet address.
6. Lock your Wallet and then refresh the page.
7. Unlock your Wallet and then click Connect
8. Click Activate and then Sign the message prompt
9. Wait for the Decrypt Message panel, Click Decrypt message to verify functionality.
10. Click Allow and it should sign you back in to pick up where you left off.

public-key-decrypt.mp4

Additional:

• Logged issue: Remove white underline from tab in dark mode on sign fragment

[SergeyZhukovsky]

++

[srirambv]

Verification passed on Oppo Reno 5 with Android 12 running 1.42.15 x64 Nightly build

• Verified test plan from PR
• Verified Encrypt and Decrypt panels are shown correctly

13868.mp4