Sovereign accounts and EVM system layer

[dmitrylavrenov]

The main goal of this pallet is to provide the opportunity to have a completely separate independent account system from native substrate system accounts. In the case when the native account system needs to work with 32 byte addresses, but EVM-compatibility with 20 byte addresses is required as well for some reason, there is a need to map these addresses, which can cause a lot of inconvenience to users and developers, since the 32 and 20 addresses are cryptographically cannot be matched 1 to 1 bijectively.

This pallet will make it possible, within one runtime, to define two independent separate account systems (native and evm), the main advantages of which are:

• no need to synthetically map 20-byte addresses with 32-byte ones
• EVM accounts can exist independently with their own logic, for example, there is no need for proper management of consumers and providers, which are needed just for the native account system.

[MOZGIII]

Let's make this PR a draft, since it is supposed to be merged after #1329 goes in.