* get conclude signal working properly; don't allocate a vector

* wip: add test suite / example / explanation for using utility subsystem

Unfortunately, the test fails right now for reasons which seem
very odd. Just have to keep poking at it.

* explicitly import everything

* fix subsystem-util test

The root problem here was two-fold:

- there was a circular dependency from subsystem -> test-helpers/subsystem ->
  subsystem
- cfg(test) doesn't propagate between crates

The solution: move the subsystem test helpers into a sub-module
within subsystem. Publicly export them from the previous location
so no other code breaks.

Doing this has an additional benefit: it ensures that no production
code can ever accidentally use the subsystem helpers, as they are compile-
gated on cfg(test).

* fully commit to moving test helpers into a subsystem module

* add some more tests

* get rid of log tests in favor of real error forwarding

It's not obvious whether we'll ever really want to chase down
these errors outside a testing context, but having the capability
won't hurt.

* fix issue which caused test to hang on osx

* only require that job errors are PartialEq when testing

also fix polkadot-node-core-backing tests

* get rid of any notion of partialeq

* rethink testing

Combine tests of starting and stopping job: leaving a test executor
with a job running was pretty clearly the cause of the sometimes-hang.

Also, add a timeout so tests _can't_ hang anymore; they just fail
after a while.

* rename fwd_errors -> forward_errors

* warn on error propagation failure

* fix unused import leftover from merge

* derive eq for subsystemerror

* Use SpawnNamed instead of Spawn in Overseer

* reexport SpawnNamed and fix doc tests

* Fix deps

* create a v1 primitives module

* Improve guide on availability types

* punctuate

* new parachains runtime uses new primitives

* tests of new runtime now use new primitives

* add ErasureChunk to guide

* export erasure chunk from v1 primitives

* subsystem crate uses v1 primitives

* node-primitives uses new v1 primitives

* port overseer to new primitives

* new-proposer uses v1 primitives (no ParachainHost anymore)

* fix no-std compilation for primitives

* service-new uses v1 primitives

* network-bridge uses new primitives

* statement distribution uses v1 primitives

* PoV distribution uses v1 primitives; add PoV::hash fn

* move parachain to v0

* remove inclusion_inherent module and place into v1

* remove everything from primitives crate root

* remove some unused old types from v0 primitives

* point everything else at primitives::v0

* squanch some warns up

* add RuntimeDebug import to no-std as well

* port over statement-table and validation

* fix final errors in validation and node-primitives

* add dummy Ord impl to committed candidate receipt

* guide: update CandidateValidationMessage

* add primitive for validationoutputs

* expand CandidateValidationMessage further

* bikeshed

* add some impls to omitted-validation-data and available-data

* expand CandidateValidationMessage

* make erasure-coding generic over v1/v0

* update usages of erasure-coding

* implement commitments.hash()

* use Arc<Pov> for CandidateValidation

* improve new erasure-coding method names

* fix up candidate backing

* update docs a bit

* fix most tests and add short-circuiting to make_pov_available

* fix remainder of candidate backing tests

* squanching warns

* squanch it up

* some fallout

* overseer fallout

* free from polkadot-test-service hell

* set up data types and control flow for statement distribution

* add some set-like methods to View

* implement sending to peers

* start fixing equivocation handling

* Add a section to the statement distribution subsystem on equivocations and flood protection

* fix typo and amend wording

* implement flood protection

* have peer knowledge tracker follow when peer first learns about a candidate

* send dependents after circulating

* add another TODO

* trigger send in one more place

* refactors from review

* send new statements to candidate backing

* instantiate active head data with runtime API values

* track our view changes and peer view changes

* apply a benefit to peers who send us statements we want

* remove unneeded TODO

* add some comments and improve Hash implementation

* start tests and fix `note_statement`

* test active_head seconding logic

* test that the per-peer tracking logic works

* test per-peer knowledge tracker

* test that peer view updates lead to messages being sent

* test statement circulation

* address review comments

* have view set methods return references