rust protover_all_supported() accepts too-long protocol names
569b4e57e23d728969a12751afc6b45f32d0f093 was fixing legacy/trac#25517 (moved) but kept the old behavior of allowing protocol names of any length for
protover_all_supported(). That's the reason this unit test was failing, and ended up being disabled on rust builds with a ??? comment of confusion.
The reason given in the commit for this behavior was
in order to maintain compatibility with consensus methods older than 29. but the corresponding C code change never made any exception like this.