largefiles: use "summaryremotehooks" to avoid redundant outgoing check Before this patch, "hg summary --remote --large" invokes "findcommonoutgoing()" not only in "commands.summary()" but also in "overrides.overridesummary()" (via "getoutgoinglfiles()"). The latter is redundant. This patch uses "summaryremotehooks" to avoid redundant outgoing check. Newly introduced function "overrides.summaryremotehook()" is registered into "summaryremotehooks" to get the result of outgoing check in "commands.summary()". It invokes "lfutil.getlfilestoupload()" directly with the result of outgoing check to avoid redundant outgoing check in "getoutgoinglfiles()".