Core: Use EmulatorBaseStore

[bblommers]

Motivation

As part of the push towards LS becoming a multi-emulator platform, one of the key features is to have a generic data + persistence layer that can be used across all emulators.
This PR is a first step in that process, using a generic data store in LocalStack (AWS).

Changes

• Introduces the EmulatorBaseStore dependency
• Overrides the BaseStore to keep the AWS-specific validation that was already in place

Testing

Running the regular test suite is enough, as there are no changes in functionality.

TODO

What's left to do:

• Review the EmulatorBaseStore project (private for now)
• Decide on the naming
• Release the EmulatorBaseStore
• Change the dependency here to use the actual release