Try to create os vpn entry whenever connect starts

[simonhong]

fix brave/brave-browser#27196

When user deletes os vpn entry while browser running, browser can't know that deletion.
So, connect again w/o creating os entry causes connect error.
To fix this, try to create os vpn entry whenever connect.
As creating os vpn entry is cheap and fast, it would not hurt UX.

Resolves

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 wiki
  • npm run lint, 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/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. Launch Brave and prepare for using vpn
2. Connect and disconnect
3. Go to system setting and delete os vpn entry
4. Connect again and check connect failed doesn't happen

[spylogsster]

++

[github-actions]

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cc: @simonhong

[stephendonner]

Verified PASSED using

Brave	1.48.55 Chromium: 108.0.5359.128 (Official Build) nightly (x86_64)
Revision	1cd27afdb8e5d057070c0961e04c490d2aca1aa0-refs/branch-heads/5359@{#1185}
OS	macOS Version 11.7.2 (Build 20G1020)

Steps

Followed my original steps to reproduce from brave/brave-browser#27196, plus additional testing.

Confirmed I could remove, and dynamically add, the BraveVPN macOS config, without the Couldn't connect to server errors popping up

Screencast