Update `/delegate` endpoints to work with typed data signatures

[DmitryBespalov]

V2 endpoints use the EIP712 signTypedData for registering the notifications.

For reference:

• Refactor delegate endpoint signatures to use EIP712 safe-transaction-service#1989
• Migrate to v2 delegate endpoints safe-client-gateway#1461

The scope of changes includes:

• changing the signing with on-device keys (imported or generated keys)
• implementing new signing request & low-level device communication with ledger devices
• sending the typed data request via wallet connect for signing (signTypedData_v4)
• using keystone's "typed data" request message
• updating the endpoints to the version 2 (getting, updating, deleting delegates)

[DmitryBespalov]

Decided to postpone migrating to the v2 because of incompatible data structure supporting only one chain_id for the same delegate address. That would lead to a signing issue where user would sign 1 request per supported network (in the worst case), or N requests according to the number of networks which safes are added in the app.

Closing this as won't fix now.

[njelich]

@DmitryBespalov So should a person trying to integrate this use the old endpoint then?

[DmitryBespalov]

@njelich for now, the v1 should work fine. New v2 endpoints would be usable once safe-global/safe-transaction-service#2081 is implemented