Changes

osmo-smdpp: Don't re-encode euiccSigned1/euiccSigned2

We used to re-encode those parts of a decoded ASN.1 struct that is
cryptographically signed in the GSMA SGP.22 specification.  However, if
the received data follows a later spec and contains new/unknown records,
then our poor-man's attempt at re-encoding will render a different
binary, which in turn means the signature check will fail.

Let's instead do a manual step-by-step raw decode of the DER TLV
structure to extract the actual binary information of parts of ASN.1
objects.

Change-Id: I4e31fd4b23ec3be15b9d07c2c30a3e31e22bdda1
Closes: OS#6473