Bug 1872920 - Change how we notify the main process when we intercept a crash via WER a=diannaS

This patch makes several fundamental changes to the logic we use to inform
the main process whenever the WER runtime exception module intercepts a child
process crash:

* We no longer read the process type or any other data from the child process;
  the process type is passed as the runtime exception module's context
* We no longer read the address of the memory area used to communicate with the
  main process from the child process arguments. Instead we allocate memory
  directly into the main process and store the required information there
* We don't read anything from the main process either, the pointer to the
  function used to notify the main process is now found by looking out its
  dedicated section in the parent process' xul.dll mapping
* We no longer read the OOM crash annotation from a child process, this
  functionality will be restored by making the module use the mozannotation
  crates to fetch all the annotations

Original Revision: https://phabricator.services.mozilla.com/D201589

Differential Revision: https://phabricator.services.mozilla.com/D202916