Refactor `gnosis_safe_proxy_factory` -> `gnosis_safe_multisig`

[jmoreira-valory]

Refactor gnosis_safe_proxy_factory -> gnosis_safe_multisig

gnosis_safe_proxy_factory is a very bad name choice. Gnosis safe proxy factory is a native Safe contract, whereas ours is called GnosisSafeMultisig.

This fix would imply renaming associated variables used in the protocol deploy method. In particular this will introduce at least a breaking change by renaming the environment variable

CUSTOM_GNOSIS_SAFE_PROXY_FACTORY_ADDRESS --> CUSTOM_GNOSIS_SAFE_MULTISIG_ADDRESS

Update

There is a contract package gnosis_safe_proxy_factory which refers to the actual proxy factory. There is a mixture of usage in the library of the concept gnosis_safe_proxy_factory (when it's correctly referenced as the Gnosis factory) and gnosis_safe_proxy_factory, when it's incorrectly referenced as the (Olas) gnosis_safe_multisig from the autonolas-registries repository.

[jmoreira-valory]

See also:
valory-xyz/olas-operate-app#643
https://github.com/valory-xyz/olas-operate-app/pull/258/files#r1702118215