Add Chain[contractAddresses] property

[iamacook]

⚠️ Depends on safe-global/safe-config-service#1175 from the Config Service.

Summary

When deploying the Safe infrastructure, it is currently necessary for a desired network to be present in our safe-deployments repo. as that is the source of truth for contract addresses.

In order to remove this hurdle, new (optional) fields for contract addresses to populate the ContractNetworksConfig of the protocol-kit for a given chain are to be added to the Config Service. This propagates the fields and validates them accordingly.

Changes

• Add new ContractAddressesSchema, include it in ChainSchema and infer a new ContractAddresses entity from it
• Add new contractAddressesBuilder and include it in chainBuilder
• Add appropriate test coverage

[coveralls]

Pull Request Test Coverage Report for Build 9936846516

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 48.129%

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Totals
Change from base Build 9858819355:	0.005%
Covered Lines:	4245
Relevant Lines:	7079

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💛 - Coveralls