Lambdas: move Contracts API to an easy to use catalyst-client implementation

[pentreathm]

The following endpoints:

/lambdas/contracts/servers
/lambdas/contracts/pois
/lambdas/contracts/denylisted-names

should be available inside catalyst-client in a way that's easy to use without adding unnecessary dependencies. Once there, we should encourage its use internally in the organization and then evaluate if we should keep them as part of the protocol (and move them to lamb2) or deprecate them.