DPP: DPPEnvelopedData parsing for Configurator backup/restore

DPP: DPPEnvelopedData parsing for Configurator backup/restore

Process the received DPPEnvelopedData when going through Configurator
provisioning as the Enrollee (the new Configurator). This parses the
message, derives the needed keys, and decrypts the Configurator
parameters. This commit stores the received information in
auth->conf_key_pkg, but the actually use of that information to create a
new Configurator instance will be handled in a separate commit.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>