fatality based errors (#4448)

* seed commit for fatality based errors

* fatality

* first draft of fatality

* cleanup

* differnt approach

* simplify

* first working version for enums, with documentation

* add split

* fix simple split test case

* extend README.md

* update fatality impl

* make tests passed

* apply fatality to first subsystem

* fatality fixes

* use fatality in a subsystem

* fix subsystemg

* fixup proc macro

* fix/test: log::*! do not execute when log handler is missing

* fix spelling

* rename Runtime2 to something sane

* allow nested split with `forward` annotations

* add free license

* enable and fixup all tests

* use external fatality

Makes this more reviewable.

* bump fatality dep

Avoid duplicate expander compilations.

* migrate availability distribution

* more fatality usage

* chore: bump fatality to 0.0.6

* fixup remaining subsystems

* chore: fmt

* make cargo spellcheck happy

* remove single instance of `#[fatal(false)]`

* last quality sweep

* fixup

polkadot/node/subsystem-util/Cargo.toml

@@ -13,6 +13,7 @@ parity-scale-codec = { version = "3.0.0", default-features = false, features = [
 pin-project = "1.0.9"
 rand = "0.8.5"
 thiserror = "1.0.30"
+fatality = "0.0.6"
 tracing = "0.1.31"
 derive_more = "0.99.17"
 lru = "0.7.2"
@@ -38,4 +39,3 @@ log = "0.4.13"
 polkadot-node-subsystem-test-helpers = { path = "../subsystem-test-helpers" }
 lazy_static = "1.4.0"
 polkadot-primitives-test-helpers = { path = "../../primitives/test-helpers" }
-