fix: password-protect account private key reveal

[josheleonard]

Resolves brave/brave-browser#24322

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:

1. Unlock the Brave wallet
2. Navigate to Accounts -> Select Account1 -> Account details -> Private Key
3. "Show key" button should be disabled & and password field should be visible
4. Enter wallet password into the password field
5. "Show key" button should now be enabled
   6a. Error message appears if incorrect password was entered
   6b. Key is displayed if correct password was entered

[brave-builds]

A Storybook has been deployed to preview UI for the latest push

[brave-builds]

A Storybook has been deployed to preview UI for the latest push

[brave-builds]

A Storybook has been deployed to preview UI for the latest push

[Douglashdaniel]

++

[kdenhartog]

Looks good - spotted one non-blocking thing to consider adding also.

As far as the design goes, it seems like it could be useful to allow the user to disable this as well with a settings toggle (assuming they've verified their password first), but I don't think that's something that should block this from going forward. Is that something worth considering here as well @jamesmudgett ?

[brave-builds]

A Storybook has been deployed to preview UI for the latest push