defaults: rename default.d to defaultrc to make it a valid package name "default.d" is not a valid Python package name, and it needs to be a valid package name if we want to be able to load the files from here as resources. Differential Revision: https://phab.mercurial-scm.org/D7426

local test passed
addgroupcopy test passed
clone test passed
lowlevelcopy test passed
slicing test passed
issnapshot test passed
findsnapshot test passed