Improvements for the IPFS diagnostics page brave://ipfs

[spylogsster]

Resolves brave/brave-browser#13173

• Add Restart button (speeds up applying config changes)
• If not installed, note "IPFS not installed" and button to install and start; other items should be grayed out to indicate missing functionality
• Additionally, display the Learn more about IPFS and privacy link described above (placement/appearance TBD once we know whether this diagnostic page can be included with the rest of Brave settings UI)
• Added buttons to open Web UI
• If the user has this diagnostic page open in one tab with their node stopped, and then starts their node from a different tab, this tab doesn't update unless it's reloaded.

Submitter Checklist:

• 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)
• 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:

• Open brave://ipfs and play with buttons, all buttons should work as expected
• Open 2 different windows with brave://ipfs page and try to stop/start node in one, the second one should update own status automatically