* remove v0 primitives from polkadot-primitives

* first pass: remove v0

* fix fallout in erasure-coding

* remove v1 primitives, consolidate to v2

* the great import update

* update runtime_api_impl_v1 to v2 as well

* guide: add `Version` request for runtime API

* add version query to runtime API

* reintroduce OldV1SessionInfo in a limited way

This is the first step to close
https://github.com/paritytech/polkadot/issues/4524

* session_info: v2 + migration

* use primitives::v2

* use polkadot_primitives::v2

* impl primitives::v2

* fix approval-voting tests

* fix other tests

* hook storage migration up

* backwards compat (1)

* backwards compat (2)

* fmt

* fix tests

* FMT

* do not reexport v1 in v2

* fmt

* set storage version to 1

Co-authored-by: Javier Viola <[email protected]>