largefiles: remove no more referred "getoutgoinglfiles()"

largefiles: use "outgoinghooks" to avoid redundant outgoing check Before this patch, "hg outgoing" invokes "findcommonoutgoing()" not only in "commands.outgoing()" but also in "overrides.overrideoutgoing()" (via "getoutgoinglfiles()"), when largefiles is enabled. The latter is redundant. This patch uses "outgoinghooks" to avoid redundant outgoing check. Newly introduced function "overrides.outgoinghook()" is registered into "outgoinghooks" to get the result of outgoing check in "commands.outgoing()". It invokes "lfutil.getlfilestoupload()" directly with the result of outgoing check to avoid redundant outgoing check in "getoutgoinglfiles()": "sort()" is needed, because "lfutil.getlfilestoupload()" doesn't sort the result of it. This patch also omits "if toupload is None" ("No remote repo") case, because failure of looking remote repository up should raise exception in "commands.outgoing()" before invocation of "outgoinghooks". Newly added "hg outgoing --large --graph" tests examine "outgoinghooks" invocations in "hg outgoing --graph" code path.

outgoing: introduce "outgoinghooks" to avoid redundant outgoing check This patch introduces "outgoinghooks" to avoid redundant outgoing check for "hg outgoing" in other than "commands.outgoing" (or utility functions used by it).

hg: make "_outgoing()" return peer object for remote repository This patch makes "_outgoing()" return peer object for remote repository, to avoid re-execution "expandpath()", "parseurl()", and "peer()" on caller side for specified URL.