[FEATURE] Parse Array of `flags` Objects From All Sync Sources

[toddbaert]

[FEATURE] Parse Array of flags Objects From All Sync Sources

Background

flagd needs to support flags defined in an array, as well as the previous map format.

Requirements

• [x] Flags must be parsed, and stored in memory, annotated with both their flagSetId (nil is a possible flagSetId) as well as their source
• [x] Refactors to the underlying storage layers are encouraged (this was mostly done with (https://github.com/open-feature/flagd/pull/1697).
• [ ] Particular care should be taken to make retreival of sets of flags based on their flag set efficient and easy
• [ ] Associated tests

See parent issue for more background.

[toddbaert]

I'm assigning this to myself; probably won't complete it but at least doing a PoC.