Move window.chrome.braveSkus to use gin

[bsclifton]

Description

Follow up from brave/brave-core#10847
(similar to #19909)

Goal would be to eliminate the boiler plate code in brave/components/skus/renderer/skus_js_handler.cc by using gin::Wrappable

As an example:
NetErrorPageController
anything that includes object_template_builder.h

return gin::Wrappable<NetErrorPageController>::GetObjectTemplateBuilder(
             isolate)
      .SetMethod("downloadButtonClick",
                 &NetErrorPageController::DownloadButtonClick)
      .SetMethod("reloadButtonClick",
                 &NetErrorPageController::ReloadButtonClick)
      .SetMethod("detailsButtonClick",
                 &NetErrorPageController::DetailsButtonClick)
      .SetMethod("diagnoseErrorsButtonClick",
                 &NetErrorPageController::DiagnoseErrorsButtonClick)
      .SetMethod("trackEasterEgg", &NetErrorPageController::TrackEasterEgg)
      .SetMethod("updateEasterEggHighScore",
                 &NetErrorPageController::UpdateEasterEggHighScore)
      .SetMethod("resetEasterEggHighScore",
                 &NetErrorPageController::ResetEasterEggHighScore)
      .SetMethod("launchOfflineItem",
                 &NetErrorPageController::LaunchOfflineItem)
      .SetMethod("launchDownloadsPage",
                 &NetErrorPageController::LaunchDownloadsPage)
      .SetMethod("savePageForLater", &NetErrorPageController::SavePageForLater)
      .SetMethod("cancelSavePage", &NetErrorPageController::CancelSavePage)
      .SetMethod("listVisibilityChanged",
                 &NetErrorPageController::ListVisibilityChanged);

[stephendonner]

Verified PASSED using

Brave	1.42.62 Chromium: 103.0.5060.114 (Official Build) beta (x86_64)
Revision	a1c2360c5b02a6d4d6ab33796ad8a268a6128226-refs/branch-heads/5060@{#1124}
OS	macOS Version 11.6.7 (Build 20G630)

Steps:

1. installed 1.42.62
2. launched Brave
3. set the appropriate SKU SDK and VPN flags in brave://flags
4. restarted Brave
5. loaded account.brave.software (development)
6. entered basic auth
7. purchased VPN
8. confirmed when prompted to add BraveVPN's config
9. confirmed my BraveVPN connection was working

example	example	example	example

---

Verification PASSED on

Brave | 1.42.78 Chromium: 103.0.5060.134 (Official Build) beta (64-bit)
-- | --
Revision | 8ec6fce403b3feb0869b0732eda8bd95011d333c-refs/branch-heads/5060@{#1262}
OS | Windows 10 Version 21H2 (Build 19044.1826)

• Verified till step 7, after purchasing the VPN we won't get prompt on window, screens which we get after VPN purchase and click on Refresh brave vpn are listed below:
• After clicking on Refresh brave vpn VPN gets auto-connected to nearest host for my region
• Click on VPN shows the connected host name

example	example	example	example

[LaurenWags]

Updated label to release-notes/exclude after conferring with @rebron as Brave VPN is not part of the 1.42.x release.