Remove pcepy from Carbon

Pcepy is the only Python code in Bgpcep repository. Since the initial code drop [0], no functional change was made, but there were multiple changes to satisfy bgpcep-veryfy-python-

job requirements (pep8 checks are growing strictier over time).

The code was never used in ODL distribution or CSIT, it is unknown whether the code is even compatible with current ODL behavior. Overall, I think it is not worth keeping the code around anymore.

There may be downstream consumers, and pcepy may be subject to API lifecycle requirements (deprecate first, delete in next release). But maybe pcepy was intended to be a part of integration test which never materialized (as far as I know), in which case it can be deleted already in Carbon.

[0] https://git.opendaylight.org/gerrit/2477