Starting with compute_linear()

Removing some indirections

Controls whether deep PLC is enabled

No dependency on the data files if no DNN code enabled

Signed-off-by: Jean-Marc Valin <jmvalin@amazon.com>

Signed-off-by: Jean-Marc Valin <jmvalin@amazon.com>

When ready, change DRED_EXTENSION_ID to the final ID, remove
DRED_EXPERIMENTAL_VERSION completely, and change DRED_EXPERIMENTAL_BYTES
to zero (eventually remove it).

Also, don't code DRED that's redundant with the main packet

Should make synthesis easier in the future

So it can be used outside of the SILK PLC

output() renamed to decode(), dred objects using alloc() and free(),
OpusDRED now passed as cost for decoding.

Makes shallow copy of decoder possible again

progressive decode, avoid storing DRED decoder state