Update to schnorrkel 0.8.0 (#3267)

* Update to schnorrkel `0.8.0`

* Increase `spec_version`

* Bump schnorrkel to 0.8.3 (#3283)

* Schnorrkel 0.8.1 (builds on bkchr upgrade branch)

* Add tests for known hard/soft derivation values

* Bump all schnorrkel versions

* Flatten for easier inspection

* 0.8.2

* 0.8.3

* Update subkey/Cargo.toml

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Update `Cargo.lock`

* 0.8.4

* Fix cargo lock file.

* Adding an error message for `NotMarkedSchnorrkel` as that was missing.
Also fixing a typo, strage -> stage.

substrate/core/consensus/babe/Cargo.toml

@@ -28,7 +28,7 @@ futures01 = { package = "futures", version = "0.1" }
 futures-timer = "0.2.1"
 parking_lot = "0.8.0"
 log = "0.4.6"
-schnorrkel = "0.1.1"
+schnorrkel = { version = "0.8.4", features = ["preaudit_deprecated"] }
 rand = "0.6.5"
 merlin = "1.0.3"