Generate legacy value contructors for all classes
This expands legacy constructor compatibility to also include
Key classes, not only value wrappers. The codegen parts is relatively
straightforward.
IdentitiableItemCodec is coded on the assumption there are only
two constructors -- one copy and one all-value, which is now violated.
Hence we update IdentifiableItemCodec to also ignore any constructors
which are marked as deprecated.
JIRA: MDSAL-330
Change-Id: Ie23ba8b3788b320b2d11e263c9af228b4c2e41a9
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>