sidedata: simply read p2copies files from the `ChangingFiles` object

sidedata: simply read p1copies files from the `ChangingFiles` object

sidedata: simply read removed files from the `ChangingFiles` object

sidedata: simply read added files from the `ChangingFiles` object

sidedata: add a `decode_files_sidedata` function Right now the function mostly gather existing code to build a consistent object. However having this function allow us prepare all user code independently from the actual side data format change (and associated encoding/decoding changes) Strictly speaking, we could not need to passe the sidedata explicitly since we have access to it though the `changelogrevision` object. However, the short term goal is to drop that first parameter to only pass the sidedata binaries.

changelog: add a `changes` property on `changelogrevision` For the sidedata storage we are moving toward "all in one" block containing the equivalent of a "ChangingFiles" instance. We do various refactoring beforehand to prepare the usage of theses new data in the code. Since the object use slots, the "property cache" tricks cannot be used, and we cache the value manually.

sidedata: rename `encode_copies_sidedata` to `encode_files_sidedata` We are storing more than copies information, so lets make it clear.

log: pass around --rev option by walkopts

log: parse --limit option by logcmdutil.parseopts()

log: pass around --follow/--follow-first options by walkopts