Create Flux daemon to serve v2 API backed by InfluxDBv3

This issue is a catchall for the moment to track interest and community efforts to update Flux to use InfluxDB 3.0 as a back end. We anticipate that the best way to do this will be to update the core Flux engine to use 3.0's FlightSQL API. This is likely not a small effort and will require changes to how the Flux planner and optimizer work.

The [Flux repo is here under a permissive MIT license](https://github.com/influxdata/flux). We've also created a [community Flux repo](https://github.com/InfluxCommunity/flux) that can be owned by the community for this effort. We think this will enable people to move more quickly without having to push things through our production code process (which would happen for anything landing in the main Flux repo).

Start by reviewing the Flux repository and the community Flux repository, then map the proposed InfluxDB 3.0 FlightSQL backend to the Flux core engine, planner, and optimizer. Done would require a defined implementation plan for the v2 API daemon and agreement on the necessary planner and optimizer changes; this issue is a catchall rather than a file-level task.

Written by the indexing model from the issue text.