Refactor: schemas: Mark invalid date rule attributes for future removal

Some elements that we have to keep in the schema (for backward
compatibility) for date_spec and duration are invalid and should be
removed later. Mark them as such.

Also reorder the valid attributes in a more coherent manner that aligns
with the order in which we process them.

Ref T196

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>