[#740] Move `AsRPC` from `morley-client` to `morley`

Description

Some of the separate projects (morley-ledgers, segmented-cfmm, etc.) need to bring in morley-client and all of its dependencies for the sole purpose of defining/deriving AsRPC instances. Ideally, those projects should not depend on morley-client.

This moves AsRPC module from morley-client to morley.

Related issue(s)

Resolves #740 (closed)

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