Design stellar integration testing library

[tamirms]

Spike to come up with a proposal for an integration testing library that can spin up ephemeral standalone networks for the purposes of testing downstream systems. This testing library can be modeled after what we currently use for horizon integration tests. Potential use cases for this library are:

• horizon integration tests
• rpc integration tests
• galexie integration tests
• integration tests downstream of horizon / rpc

The library should provide the option of spinning up a core validator and (optionally) horizon / rpc

[sreuland]

this may be able to use the new quickstart build and run callable GH CI workflows for provisioning ad-hoc standalone network instances, included links of that usage as an example from system-test