VPN should have a right click to hide

[bsclifton]

Test plan

On macOS and Windows only (VPN not available on Linux)

1. Set brave://flags/#brave-vpn to ENABLED
2. Set brave://flags/#skus-sdk to ENABLED
3. Restart the browser
4. Verify the VPN button shows next to Hamburger menu
5. Right click the VPN button
6. You should see the menu:
   
7. Pick the "Hide VPN button in toolbar" option
8. VPN button should disappear

Description

If VPN is enabled, some users may not want to see it.

It would be great if they can right click (or ctrl+click) the VPN icon:

And then we can have a context menu show Hide VPN button. This would do the same thing as when you go into settings and using the toggle under appearance:

[stephendonner]

Verified PASSED using

Brave	1.37.60 Chromium: 99.0.4844.35 (Official Build) nightly (64-bit)
Revision	f60a827ddb87f1c403e07713751a5551d5856ac0-refs/branch-heads/4844@{#579}
OS	Windows 10 Version 21H2 (Build 19044.1566)

Confirmed:

• can disable VPN button via context-menu option Hide VPN button in toolbar
• can enable/disable VPN button via Show VPN button toggle in brave://settings/appearance
• top-level Brave VPN menu item is available regardless of the toggle state, above
• clicking both the menu item above and the VPN button on the toolbar launch the onboarding doorhanger dialog

example	example	example	example	example

example	example	example

[bsclifton]

Quick update - we won't be able to test this on Beta until brave/brave-core#12175 is merged (see #21598)

[stephendonner]

Quick update - we won't be able to test this on Beta until brave/brave-core#12175 is merged (see #21598)

Setting QA/Blocked so we know to hold off until the above is resolved.

[LaurenWags]

Removing QA/Test-All-Platforms as this is not available on Linux. The OS/Windows and OS/macOS labels will suffice to ensure this is checked on the appropriate platforms.

[stephendonner]

1. Clearing QA Pass-Win64 as this will need to be re-verified using 1.38.x or later.
2. Settings milestone to 1.38.x as per today's desktop meeting

[LaurenWags]

Changing to QA/No per discussion in today's desktop planning meeting, testing will be covered with #15804.