Brave Software: Local files reading from the web using `brave://`

Brave Software introduced `brave://` protocol to replace `AsarProtocolHandler` in `brave/muon`. However, a severe bug allows reading local files from the web by using `brave://` instead of `file://`. Products affected include Brave 0.23.73, V8 6.8.275.24, rev 50bdb6df42550dd14f5636770ec8585aa26e361b, Muon 8.0.3, OS Release 17.7.0, Update Channel: Release, OS Architecture: x64, OS Platform: macOS, Node.js 7.9.0, Brave Sync v1.4.2, and libchromiumcontent 68.0.3440.75