Deprecate AbstractRpcService and RpcServiceRequestable

[mcmire]

Explanation

In the past, AbstractRpcService and RpcServiceRequestable were added so that we could express that the fetch and Infura middleware supported either an RpcService or RpcServiceChain. However, since then, these middleware have been changed so that they do not care about a complete RPC service-like interface, just the request method. Hence, it is no longer necessary for the two interfaces to exist.

In fact, the existence of these interfaces create impediments for development. RpcService is not public itself, but AbstractRpcService and RpcServiceRequestable are. So each time we make incompatible changes to RpcService we have to remember to keep AbstractRpcService and RpcServiceRequestable updated as well, and this results in more major releases for network-controller than we would like.

To address these issues, we update RpcService so that it no longer implements AbstractRpcService, and we deprecate both interfaces so that we do not have to update them whenever we make changes to RpcService or RpcServiceChain. We will remove both interfaces in a future major version.

References

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Medium Risk
Public TypeScript surface changes deprecate exported RPC service interfaces and stop RpcService from implementing them, which may affect downstream typing even though runtime behavior is unchanged.

Overview
Marks the exported AbstractRpcService and RpcServiceRequestable types as deprecated (with guidance to accept narrower “RPC-like” shapes), and records this deprecation in the network-controller changelog.

Updates RpcService to no longer implement AbstractRpcService and replaces interface-derived listener typings/return types with explicit ServicePolicy-based types from ./shared, removing the cockatiel IDisposable dependency.

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