Emit Event with Salt Nonce on Proxy Creation

[nlordell]

Context / issue

For indexing purposes, it would be useful to, in addition to the currently emitted information when deploying new Safe proxies, the salt nonce would also be provided. This would allow the transaction service to index the salt nonce on newly created Safes.

Proposed solution

Add a new field to the proxy creation event that includes the salt nonce.

Alternatives

In order to remain backwards compatible - we can emit an additional event including the salt nonce. This way, the existing ProxyCreated event doesn't change.