deps: use polkadot-sdk umbrella crate (#1786)

* deps: unify usage of polkadot-sdk crates

* cargo fmt

* fix macro crate

* make tests compile

* fix more nits

* fix doc tests

* fix more nits

* more nits

* core: remove polkadot-sdk/std

* cargo fmt

* remove polkadot-sdk/std by default

* Update metadata/Cargo.toml

* remove more std

* Update Cargo.toml

signer/src/crypto/derive_junction.rs

@@ -3,6 +3,7 @@
 // see LICENSE for license details.
 
 use codec::{Decode, Encode};
+use polkadot_sdk::sp_crypto_hashing;
 
 // This code is taken from sp_core::crypto::DeriveJunction. The logic should be identical,
 // though the API is tweaked a touch.