[hooks/syncschema] make sure CWUniqueTogetherConstraintDelOp happens before CWConstraintDelOp SQLServer refuses to index an unlimited text column, so we should drop unique_together constraints (which imply an index) before we drop size constraints. Closes #5560601.

[hooks/syncschema] only call "ALTER TABLE" once when changing a size constraint Until now we would: - remove the old size constraint from the in-memory schema - call update_rdef_column which removes the size restriction from the column's type - add the new constraint object - call update_rdef_column which adds the size restriction back This breaks on SQL Server when the column is involved in an index (e.g. as part of a multi-column unique constraint), because in the intermediate stage the column's type is "nvarchar(max)", which is not indexable. Of course we must still detect the case where a size constraint is really dropped and update the db schema accordingly. Closes #5557633.

[syncschema] only add to the `synchronized` set if all possible updates have been done Otherwise a simple sync_schema(syncprops=False) turns the subsequent sync_schema() calls into a no-op. Closes #6510918.

[qunit] remove unused 'data_files' parameter Its use was removed when we stoppped pointing firefox at file:// web/test/jstests/ajax_url2.html has never actually been used, it's only been ever mentioned in a QUnit comment.

[urlpublish] RESTPathEvaluator now use vid_from_rset This avoid cases where vid may be unexpectedly overwritten. For instance when you define a custom vid for a mime type in VID_BY_MIMETYPE, it will currently be overriden by the URL publisher when you access to /<etype> with the proper Accept header. To do so, a new 'check_table' argument is introduced, which may cause bw compatibility problems if the function has been monkey-patched. Also pep8 a bit the tests. Closes #5705835

[server/sources] use decode_extid in datafeed

[server/sources] add decode_extid method avoids having the same dance in both eid_type_source variants

[server/repo] kill repo.pinfo() session.cnxset is dead, this can't work.

[web/sessions] simplify session cleanup session.cnx.check() is no longer a thing. It dates back to dbapi.

[server/repo] fix typo