Changes

utils: Introduce BER-TLV parsers that return raw tag or even raw TLV

In the eSIM RSP univers there are some rather ugly layering violatoins
where ASN.1 cannot be parsed but we have to mess with raw TLVs and the
details of DER encoding.  Let's add two funtions that make it more
convenient to work with this: They return the raw tag as integer, or
even the entire encoded TLV rather than the value part only.

Change-Id: I1e68a4003b833e86e9282c77325afa86ce144b98