Chromium Site Isolation - Legacy Binding Test failure

Commit https://github.com/cefsharp/CefSharp/commit/221185bf28b8cd4654e6ab1eb59897d372bf41c0 enabled site isolation by default for `master`

Tests are passing with the exception of [IntegrationTestFacts.LoadLegacyJavaScriptBindingQunitTestsSuccessfulCompletion](https://ci.appveyor.com/project/cefsharp/cefsharp/builds/41224952#L274). Same test passes when I run it through `Visual Studio Test Explorer`. A new issue should be created and debugged at some point to determine the cause and evaluate if it's fixable or if `upstream` changes are required.

_Originally posted by @amaitland in https://github.com/cefsharp/CefSharp/issues/2967#issuecomment-948229141_

Iniziate con IntegrationTestFacts.LoadLegacyJavaScriptBindingQunitTestsSuccessfulCompletion e confrontate il fallimento di AppVeyor nella build 41224952 con lo stesso test in Visual Studio Test Explorer. Determinate se Chromium site isolation causa il fallimento, quindi documentate se CefSharp può risolverlo o se è necessaria una modifica upstream.

Scritto dal modello di indicizzazione a partire dal testo della issue.