merge.applyupdates: extend action queues with ones returned from mergestate These queues will always be empty at the moment -- we're going to fill them up in upcoming patches.

mergestate: add a method to compute actions to perform on dirstate We're going to use this to extend the action lists in merge.applyupdates. The somewhat funky return value is to make passing this dict directly into recordactions easier. We're going to exploit that in an upcoming patch.

merge.applyupdates: use counters from mergestate This eliminates a whole bunch of duplicate code and allows us to update the removed count for change/delete conflicts where the delete action was chosen.

mergestate: add a function to return the number of unresolved files Note that unlike the other functions, this is based on the persistent mergestate.

mergestate: add a method to return updated/merged/removed counts This will not only allow us to remove a bunch of duplicate code in applyupdates in an upcoming patch, it will also allow the resolve interface to be a lot simpler: it doesn't need to return the dirstate action to applyupdates.

mergestate._resolve: don't return the action any more This is a partial backout of an earlier diff -- now that we're storing the results in a dict, we don't actually need this any more.

mergestate._resolve: store return code and action for each file We're going to need this to compute (a) updated/merged/unresolved counts, and (b) actions to perform on the dirstate.

revsetbenchmarks: support benchmarking changectx loading Many revset consumers construct changectx instances for each returned result. Add support for benchmarking this to our revset benchmark script. In the future, we might want to have some kind of special syntax in the parsed revset files to engage this mode automatically. This would enable us to load changectxs for revsets that do that in the code and would more accurately benchmark what's actually happening. For now, running all revsets with or without changectxs is sufficient.