1. A system, comprising a plurality of computing devices configured to implement: a plurality of computing platform resources of a provider network, wherein each computing platform resource of at least a subset of the plurality of computing platform resources is assignable to a client account of a client of the provider network; a plurality of service managers, wherein each service manager of the plurality of service managers is configured to coordinate a respective distributed network-accessible service of a plurality of services implemented at least in part using computing platform resources of the provider network; and a metadata manager, wherein the metadata manager is configured to: collect information from each service of a set of services of the plurality of services to determine a representation of an administrative state of the set of services, the set of services used by a client account, wherein the representation comprises a first set of configuration settings of an original set of computing platform resources of the plurality of computing platform resources configured to provide at least a portion of a functionality of the set of services to the particular source client account, wherein the administrative state provides a unified view of the administrative state across multiple services of the set of services of the client account; implement one or more interfaces to allow a submission of an account cloning request; and in response to receipt of an account cloning request in accordance with the one or more interfaces, the account cloning request specifying the client account as a particular source client account of the client of the provider network and specifying a particular version descriptor, identify the representation of the administrative state of the particular source client account with respect to each service of the set of services of the plurality of services, wherein the representation comprises the first set of configuration settings of the original set of computing platform resources of the plurality of computing platform resources configured to provide at least the portion of the functionality of the set of services to the particular source client account at a time indicated by the particular version descriptor; and store a record of an association of a clone client account of the particular source client account with the representation of the administrative state.