This patch implements all changes to the specification touching the
subset of module script fetching we support.
Notably it adds parts of the specification for supporting import maps.
With this we are also able to get rid of a non standard workaround for a
spec issue we discovered while initially implementing module scripts :^)
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>
