Make InvalidFrameEnd inherit from FrameDecode

[kickster97]

Describe the solution you'd like
Currently Error::FrameDecode and Error::InvalidFrameEnd are sibling classes, both inheriting directly from Error. An invalid frame end is semantically a frame decode error, so InvalidFrameEnd should inherit from FrameDecode.

This would simplify rescue clauses in lavinmq, e.g. in client.cr we currently need:

rescue ex : AMQ::Protocol::Error::FrameDecode | AMQ::Protocol::Error::InvalidFrameEnd

With the inheritance change, catching FrameDecode would be sufficient.