Hook hgdemandimport to fix Mercurial in intercepted terminals

Without this, 'hg' fails with:

ModuleNotFoundError: No module named 'http.cookiejar

Not totally clear why, but it's fairly clearly an interaction between
our funky import hooks and their funky import hooks. This module
appears to be a startup time optimization, and it's certainly optional
(there's an env var to disable it, and a built-in list of modules it
doesn't support) so best to just no-op it's enable() function.

Author: pimterry

overrides/pythonpath/hgdemandimport.py

@@ -0,0 +1,12 @@
+from httptoolkit_intercept import preload_real_module
+
+preload_real_module('hgdemandimport')
+
+import hgdemandimport
+
+# Re-export all other public fields
+from hgdemandimport import *
+
+# Disable hgdemandimport entirely. This is an optional optimization used by hg, which doesn't play
+# nicely with HTTP Toolkit's import hooks, making hg unusable.
+hgdemandimport.enable = lambda: None