Merge branch 'devnet5' into feat/integrate-leanmultisig-devnet5

Resolves conflicts from devnet5's leanMultisig/leansig bump (#387) against
this branch's leanMultisig devnet5 integration. Keep lean-multisig and
leansig_wrapper at 0242c909 (leanMultisig devnet5 branch); leansig stays
on the devnet4 branch to mirror leanMultisig 0242c909's own pin and keep
one leansig copy in Cargo.lock. Drop the local LeanSignatureScheme alias
in crypto tests in favor of the import already provided by
ethlambda-types, and adopt the SIGAborting* rename in types/signature.rs
(both leansig branches carry it now).

Author: MegaRedHand