[Utility] Support configuring of acceptable payload format(s) for each service

[adshmh]

Objective

Support configuration of acceptable payload format(s) for each service, e.g. JSONRPC for Ethereum relay chain.

Origin Document

Part of work on #860

The client, should support configuration that specifies the payload format for each service: this will eliminate the need for the oversimplified approach of deserializing the payload until it matches a format.

Goals

• Avoid sending any relays that are clearly invalid due to format mismatch with the target service.

Deliverable

• The client binary should allow configuration of accepted payload format(s) for each service
• The client binary should have a default set of mappings indicating service -> accepted payload format(s).
• Updated documentation describing the behavior change and how to update the default configuration.
• Updated Validation diagrams, e.g. the Client-side Relay Validation diagram

Non-goals / Non-deliverables

• A thorough validation of the relay contents based on the target service

General issue deliverables

• Update any relevant local/global README(s)
• Update relevant source code tree explanations
• Add or update any relevant or supporting mermaid diagrams

Testing Methodology

• Task specific tests or benchmarks: make ...
• New tests or benchmarks: make ...
• All tests: make test_all
• LocalNet: verify a LocalNet is still functioning correctly by following the instructions at docs/development/README.md
• k8s LocalNet: verify a k8s LocalNet is still functioning correctly by following the instructions here

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Creator: [@adshmh]
Co-Owners: [@Olshansk]