Allow Multisend calls

[llunaCreixent]

The delegate call cannot be estimated through the relayer (see https://github.com/safe-global/safe-eth-py/blob/master/gnosis/safe/safe.py#L800).

In local environment with docker it works, but not in production.
We need to enable the feature in the relayer.

As an example of how to do it, let's see the case of using Multisend to update safe version and change fallback handler.
Check tx data in the gnosis ap ui, both estimations are attempted: first from the Safe and then directly from the owner account.