This patch adds a non standard step pushing the realm execution context
of fetching client's settings object onto the execution context stack
before linking a module script. Without the realm execution context
there is no current settings object, leading to a crash in
HostResolveImportedModule.
This patch adds various algorithms required to fetch and link module
scripts.
Some parts such as actually creating a request and error handling are
not implemented or use temporary non spec compliant code to get us
further.
Co-authored-by: davidot <davidot@serenityos.org>
