copies: directly pass a changes object to the copy tracing code The object contains all the data we need. For example, the `is_merged` callback can now use the associated precomputed data. This will be useful again soon when the `salvaged` set will be introduce to solve the issue with delete file reverted during a merge. See 4b582a93316a and 14be07d5603c for details. Differential Revision: https://phab.mercurial-scm.org/D9117

copies: no longer change the sidedata flag With the new sidedata storage that include data about all file changes, every revision has one, so the sidedata flag is not longer a good way to spot changeset with copy information. So we drop this check to simplify the code We optimisation itself provided an interesting speedup, so we will likely reintroduce something similar, with a dedicated flag, in the future. Differential Revision: https://phab.mercurial-scm.org/D9116

copies: use dedicated `_revinfo_getter` function and call We want to return data in a different form, so we need different revinfo function. At that point it make sense to have different getter. Differential Revision: https://phab.mercurial-scm.org/D9115