config: add a .hg/hgrc-not-shared which won't be shared in share-safe mode Previous patches add a safe mode for sharing repositories which involve sharing of source requirements and config files. In certain situations we might need to add a config to source repository which we does not want to share. For this, we add a `.hg/hgrc-not-shared` which won't be shared. This also adds a `--non-shared` flag to `hg config` command to see the non-shared config. Differential Revision: https://phab.mercurial-scm.org/D8673