RUSTSEC-2021-0076 bump libsecp256k1 (#9391)

* RUSTSEC-2021-0076 bump libsecp256k1

libsecp256k1 allows overflowing signatures
https://rustsec.org/advisories/RUSTSEC-2021-0076

Changes were made to conform to libsecp256k1 version differences.

Closes #9356

* parse_standard_slice() -> parse_overflowing_slice()

* Added v2 host function for ecdsa_verify

* Add feature tag over helpers

* Added ecdsa_verify v2 to test runner

* PR feedback

- Spaces -> tabs
- renamed two helper functions

* Fixed imports after rebasing

* Bump rest of libsecp256k1 (and libp2p)

libp2p also uses libsecp256k1 so it is required to be bumped too, along
with all the version difference changes.

* Add version2 for ecdsa pubkey recovery

* libp2p rebase master fixes

* Fix test panic when non Behaviour event is returned

* Update bin/node/browser-testing/Cargo.toml

* Update primitives/core/src/ecdsa.rs

* Update primitives/core/src/ecdsa.rs

* Update Cargo.lock

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/client/executor/Cargo.toml

@@ -32,7 +32,7 @@ sc-executor-wasmi = { version = "0.10.0-dev", path = "wasmi" }
 sc-executor-wasmtime = { version = "0.10.0-dev", path = "wasmtime", optional = true }
 parking_lot = "0.11.1"
 log = "0.4.8"
-libsecp256k1 = "0.3.4"
+libsecp256k1 = "0.6"
 
 [dev-dependencies]
 wat = "1.0"