script: Add support for creating globals in isolated compartments (#38236)

to use the [SpiderMonkey Debugger
API](https://firefox-source-docs.mozilla.org/js/Debugger/), we need to
call it from an internal debugger script that we will supply. this
script must run in the same runtime as the debuggee(s), but in a
separate
[compartment](https://udn.realityripple.com/docs/Mozilla/Projects/SpiderMonkey/Compartments)
([more
details](https://hacks.mozilla.org/2020/03/future-proofing-firefoxs-javascript-debugger-implementation/)).

when creating two globals in the same runtime, Servo will generally try
to reuse an existing compartment for the second global, and there are
other places in script where we rely on this reuse. but for the debugger
script, we can’t do this.

this patch adds a `use_system_compartment` flag to global object
descriptors, which isolates the global in its own compartment in both
possible directions:
- it forces the global to create a new compartment, preventing the reuse
of any debuggee’s compartment
- it fails the check in select_compartment(), preventing future
debuggees from reusing the global’s compartment

Testing: manually tested working in devtools debugger patch (#37667),
where it will undergo automated tests

---------

Signed-off-by: Delan Azabani <dazabani@igalia.com>
Co-authored-by: atbrakhi <atbrakhi@igalia.com>

components/script_bindings/codegen/configuration.py

@@ -252,6 +252,7 @@ class Descriptor(DescriptorProvider):
         self.outerObjectHook = desc.get('outerObjectHook', 'None')
         self.proxy = False
         self.weakReferenceable = desc.get('weakReferenceable', False)
+        self.useSystemCompartment = desc.get('useSystemCompartment', False)
 
         # If we're concrete, we need to crawl our ancestor interfaces and mark
         # them as having a concrete descendant.