services: rpc service

[daniel-burghardt]

What

Creates a new RPC service, extracting the logic from the TSS package into a more general one to be available and used across the application.

Why

The Ingest Service for the new Balances Ingestion feature will also require RPC communication, therefore the RPC functions are being extracted into its own service.

Known limitations

N/A

Issue that this PR addresses

[Wallet Backend] Refactor RPC code into a separate service

Checklist

PR Structure

• It is not possible to break this PR down into smaller PRs.
• This PR does not mix refactoring changes with feature changes.
• This PR's title starts with name of package that is most changed in the PR, or all if the changes are broad or impact many packages.

Thoroughness

• This PR adds tests for the new functionality or fixes.
• All updated queries have been tested (refer to this check if the data set returned by the updated query is expected to be same as the original one).

Release

• This is not a breaking change.
• This is ready to be tested in development.
• The new functionality is gated with a feature flag if this is not ready for production.

[gouthamp-stellar]

This mostly looks good to me aside from the tiny comments, let me know when you have the tests running and I'll take another look