sidedata: replace sidedata upgrade mechanism with the new one Note: this is split into a separate change (like some other patches in this series) because it's not easy to have all patches work 100% and this seemed easier for reviewers. When cloning or upgrading a repo, we may need to compute (or remove) sidedata. This is the same mechanism that is used in exchange, so we re-use the new system to simplify the code and fix the remaining issues (correctly dropping flags and handling partial removal, etc.). This also highlighted an issue with `test-copies-in-changeset.t` that kept sidedata categories that are not relevant anymore. They should probably be dropped entirely, but that would be for another patch. Differential Revision: https://phab.mercurial-scm.org/D10359

--- a/tests/test-copies-in-changeset.t	Mon Apr 19 11:22:21 2021 +0200
+++ b/tests/test-copies-in-changeset.t	Mon Apr 19 11:22:24 2021 +0200
@@ -419,7 +419,7 @@
 Test upgrading/downgrading to sidedata storage
 ==============================================
 
-downgrading (keeping some sidedata)
+downgrading
 
   $ hg debugformat -v
   format-variant     repo config default
@@ -465,11 +465,7 @@
   compression:        zstd   zstd    zstd (zstd !)
   compression-level:  default default default
   $ hg debugsidedata -c -- 0
-  1 sidedata entries
-   entry-0014 size 14
   $ hg debugsidedata -c -- 1
-  1 sidedata entries
-   entry-0014 size 14
   $ hg debugsidedata -m -- 0
 
 upgrading