Incorporates the latest changes to the light client sync protocol based
on Devconnect AMS feedback. Note that this breaks compatibility with the
previous prototype, due to changes to data structures and endpoints.
See https://github.com/ethereum/consensus-specs/pull/2802
* "official" -> "scenarios", like the submodule
* fewer test binaries - various compile hacks have been improved over
time, test suite should follow
* remove obsolete bls tests - there are better test vectors in
nim-blscurve
* remove obsolete mentions of `ssz_testing`
* remove obsolete comments about proc vs globals, unittest2 already uses
proc's
Etan Kissling
tersec
Jacek Sieka