src: bootstrap Web [Exposed=*] APIs in the shadow realm
This is the initial work to bootstrap Web interfaces that are defined
with extended attributes [Exposed=*].
The ShadowRealm instances are garbage-collected once it is unreachable. However, V8 can not infer the reference cycles between the per-realm strong persistent function handles and the realm's context handle. To allow the context to be gc-ed once it is not reachable, the per-realm persistent handles are attached to the context's global object and the persistent handles are set as weak.