The send_apdu* methods now support lchan patching, so there is no longer
a need for computing the class byte manually (which is prone get forgotten)
before calling a send_apdu*. It is now enough to supply an APDU that has
a class byte with the default channel selected. This also means we do not
need cla4lchan anymore, so let's restruture the code and get rid of it
completely.
Related: OS#6531
Change-Id: Ia795f3c16a8875484fce3b44e61497d5aa52b447