dirstate-v2: Swap the order of size and mtime on disk
This makes the dirstate-v2 file format match dirstate-v1 for the order of
`mode`, `size`, and `mtime`. This order does not matter as long as these
components are handled through named fields/attributes in code, but in a few
places we still have tuples so having the same order everywhere might help
avoid a bug that might not be obvious since those components have the same type.
Differential Revision: https://phab.mercurial-scm.org/D11620
$ rm -rf a
$ hg init a
$ cd a
$ echo a > a
$ hg ci -Am0
adding a
$ hg tag t1 # 1
$ hg tag --remove t1 # 2
$ hg co 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg tag -f -r0 t1
$ hg tags
tip 3:a49829c4fc11
t1 0:f7b1eb17ad24
$ cd ..