* Introduce keystore specialized sign methods
* Get rid of 'AppKey::UntypedGeneric' associated type.
Untyped generics are accessible using associated types 'Generic' associated type.
I.e. <T as AppKey>::Public::Generic
* Get rid of 'CryptoTypePublicPair'
* Trivial fix
* Small refactory of local keystore implementations
* Remove 'crypto_id' method from 'Public'
* Trivial rename of 'AppKey' to 'AppCrypto'
* Remove unused import
* Improve docs
* Better signature related errors for authority-discovery
* Apply review suggestion
* Apply review suggestions
Co-authored-by: Koute <koute@users.noreply.github.com>
* Authority discoverty signing error revisited
* Signing error revisited for babe and aura as well
* Further cleanup
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Co-authored-by: Koute <koute@users.noreply.github.com>