Aligns brave:// with chrome:// in IntentHandler.intentHasUnsafeInternalScheme.
The upstream guard is unaware of the Brave alias because the brave:// →
chrome:// rewrite happens after the intent layer.
BraveIntentHandlerClassAdapter redirects the upstream call site through
BraveIntentHandler.intentHasUnsafeInternalScheme. The Brave method defers to
upstream first, then additionally rejects brave:// under the same category
guard upstream uses. A new BraveIntentHandlerInternal helper holds the
bytecode stub used to back-call the (private) upstream method.
Resolves: https://github.com/brave/brave-browser/issues/55473