Add core protocol version to GetNetworkResponse struct

[cjonas9]

What

This PR adds a field for the core protocol version to the GetNetworkResponse struct.

Why

• See Add Soroban interface version to getNetwork response.
• Also see this PR, which this PR is to move in lockstep with.

Known limitations

N/A

[Copilot]

Pull request overview

This PR adds support for querying Soroban network limits from stellar-core's sorobaninfo endpoint. It introduces new data structures to represent Soroban network configuration limits and protocol version information, which are then exposed through the RPC's getNetwork response.

• Adds SorobanInfoResponse struct with comprehensive Soroban network limits and configuration settings
• Implements SorobanInfo() client method to query the stellar-core sorobaninfo endpoint
• Updates GetNetworkResponse to include protocol versions and Soroban limits

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
protocols/stellarcore/info_response.go	Adds SorobanInfoResponse struct with nested structures for transaction limits, ledger limits, fees, state archival settings, and SCP settings; fixes incomplete comment on IsSynced()
protocols/rpc/get_network.go	Adds GetProtocolVersions struct and updates GetNetworkResponse to include protocol versions and Soroban limits from stellar-core
clients/stellarcore/client.go	Implements SorobanInfo() method to call stellar-core's sorobaninfo endpoint; includes minor formatting cleanup (line breaks)

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