Bug 1594529 - Create LoadInfo for subdocuments directly in parent process with DocumentChannel. r=mattwoodrow,nika

Currently, with Fission enabled we are not able to create a proper LoadInfo
object when doing a subdocument load because we do not have access to a loading
context if the load is happening inside of an OOP frame. To solve this problem,
we can create LoadInfo object from scratch in the parent process where we have
all of the required information.

Differential Revision: https://phabricator.services.mozilla.com/D68893

--HG--
extra : moz-landing-system : lando