Get region list from vpn service to webui

[nullhook]

Resolves brave/brave-browser#18055
Resolves brave/brave-browser#18402

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:

[petemill]

some questions

[nullhook]

This is failing because storybook's webpack config isn't aware of gen/ path.

await for this PR to be merged: #10056

[simonhong]

++

[simonhong]

++

[simonhong]

++

[petemill]

Wondering why we're adding new types when these seem to be in .mojom and now you're pulling in mojom types directly to './panel_browser_api'?

[nullhook]

There are state types and then there are mojom types. The mojom types will be directly pulled from m.js file in another PR and I will move all state types to another folder dir.

[petemill]

SonarCloud failure is false positive

[petemill]

Last macOS build got a timeout but we're ok to merge IMO as we've had several macOS successful builds - we did the rebuilds to fix linux via devops changes to run gn storybook targets, and now that's a success.