Extend util convert with base64 public keys

[roman-khimov]

Is your feature request related to a problem? Please describe.

I'm always frustrated when I can't easily see that AzAsKhDGXY3es9Sud1UZHlNuaIUeA8RP5L525bksW2X1 is a nice 03302c2a10c65d8ddeb3d4ae7755191e536e68851e03c44fe4be76e5b92c5b65f5 public key. And I'm also frustrated when I can't convert nice 03302c2a10c65d8ddeb3d4ae7755191e536e68851e03c44fe4be76e5b92c5b65f5 key into AzAsKhDGXY3es9Sud1UZHlNuaIUeA8RP5L525bksW2X1.

Describe the solution you'd like

Detect keys in base64 inputs, output hex and addresses. Add conversion to base64 for hex key inputs as well.

Additional context

NeoFS EACLs use base64 form, but RPC invocations can return some base64-encoded data as well.

Check base64-encoded addresses as well, not sure they're handled properly now.