Intersection with ShadowRealm API proposal

[fred-wang]

There is a PerformShadowRealmEval operation defined here:
https://tc39.es/proposal-shadowrealm/#sec-performshadowrealmeval

At minimum, the HostEnsureCanCompileStrings call will need to be tweaked to pass the new parameters defined in the Dynamic Code Brand Checks spec.

We might also want PerformShadowRealmEval to accept sourceText as Object and try to convert them to String using HostGetCodeForEval, but I'm not sure.

cc @koto