config: add a new [command-templates] section for templates defined by hg The existing `[templates]` section lets the user define their own keys and then refer to them on the command line with `-T`. There are many cases where hg wants to use a user-defined template with a given name, such as `ui.logtemplate` and `ui.mergemarkertemplate`. This patch starts moving such configs in a common section by moving `ui.logtemplate` to `command-templates.log` (with an alias from the old name, of course). Differential Revision: https://phab.mercurial-scm.org/D9245