Floss: add a member to store codec in esco_param

In anticipation of having LC3 and mSBC both qualifying for the
"transparent" coding format, we need an extra member to store which of
them is the underlying codec for various operations.

In this CL, we add a new member `coding_format` to store that.

Bug: 269970706
Tag: #floss
Test: Build and verify
Change-Id: Id4dc424b6917cd884e1ded0d38ca6f34d5cff604