dirstate: properly clean-up some more merge state on setparents

phases: move root phase assignment to it's own function This moves the initial root phase assignment to it's own function. Future patches which make phase calculations lazy will use this function to pre-fill certain phases which can be deduced from the roots.

phases: add invalidate function Phase cache invalidation was spread all over the place. Let's add a function to unify it. Later more will be added to this function.

phases: change phase command change detection A future patch is going to make phase computation lazy, so the phase command can no longer read and diff the entire phase list directly. This changes the phase command to build it's own list for diff purposes.

spanset: remove `.set()` definition All my friends are dead.

generatorset: remove `.set()` definition All my friends are dead.

addset: remove `.set()` definition All my friends are dead.

filteredset: remove `.set()` definition All my friends are dead.

baseset: remove `set()` definition All my friends are dead.

abstractsmartset: remove `set()` method definition Now that all usages have been removed, we can drop this not so useful part of the API. We can note that the name was wrong all along...

match: check if an object is a baseset using `isascending` instead of `set` The `set()` method is going away.

getset: check if an object is a baseset using `isascending` instead of `set` The `set()` method is going away.

fullreposet: detect smartset using "isascending" instead of "set" The `.set()` function is going away.

fullreposet: drop custom sets but not smartsets detection All custom classes use by revsets are smartsets now. We drop the special-casing.

addset: drop `.set()` usage during iteration We can use the containment check directly.

baseset: access `_set` directly for containment check The `.set()` method is going away.

baseset: make `_set` a property cache This will remove the need for `baseset.set()`.

graphnode: remove usage of `set()` All smartset classes have fast lookup, so this function will be removed soon.

revset-_hexlist: remove usage of `set()` All smartset classes have fast lookup, so this function will be removed soon.

revset-_intlist: remove usage of `set()` All smartset classes have fast lookup, so this function will be removed soon.

revset-_list: remove usage of `set()` All smartset classes have fast lookup, so this function will be removed soon.

revset-roots: remove usage of `set()` All smartset classes have fast lookup, so this function will be removed soon.

histedit: stabilise the order nodes that are stripped The `nodes` object is a set. We sort it to get stable order. This is going to prevent revsets from getting confused when removing a `.set()` call in `roots`.

revset-origin: remove usage of `set()` All smartset classes have fast lookup, so this function will be removed soon.

revset-last: remove usage of `set()` All smartset classes have fast lookup, so this function will be removed soon.

revset-limit: remove usage of `set()` All smartset classes have fast lookup, so this function will be removed soon.

revset-destination: remove usage of `set()` All smartset classes have fast lookup, so this function will be removed soon.

revset-children: remove usage of `set()` All smartset classes have fast lookup, so this function will be removed soon.