It implements the new codeForEvalGets callback to retrieve the
value for a trusted script object. Additionally, it implements
the new logic in can-compile-strings to call the policy
factory if required.
Note that parameter and argument checks aren't implemented yet,
as they require updates to binding generation (see TODO in
script_runtime).
Part of #36258
Signed-off-by: Tim van der Lippe <tvanderlippe@gmail.com>