Add in memory dev data store as a configuration option. This allows u…

[mwksl]

…sers to pass in small features for evaluation locally without having to connect to Launch Darkly services. This also allows easy "pull and play" configurations

Requirements

• [x] I have added test coverage for new or changed functionality
• [x] I have followed the repository's pull request submission guidelines
• [x] I have validated my changes against all supported platform versions

Related issues

N/A

Describe the solution you've provided

This allows a configuration option for feature flags to be evaluated offline in the update processor.

Describe alternatives you've considered

In-theory, you could select offline mode and provide an SDK key and file to evaluate, but this gets messy across large distributed teams. This allows us to have one LaunchDarkly config that can be easily changed across branches.

Additional context

For our release cycles, it became hard to manage multiple flags, files, and configs. This unifies configuration into the LD configuration and allows new members to pull projects and easily implement local feature flags server-side.

[mwksl]

Nevermind, we figured out how to do this with InMemoryFeatureStore.