[State] Presets with state chunk is not supported in our .FXB generator/parser

- [x] Can parse `.fxp` with chunk and non-chunks in `presetbank`
- [x] V2 Dplug chunks necessitate the `--state` flag in `presetbank`.
- [ ] Can create `.fxb` bank made of presets with state chunks
- [ ] Can parse such `.fxb` even if we generated it with `presetbank`

For now: presets with empty state will work, as a workaround.

Start at the presetbank entry point and locate the existing .fxp chunk and .fxb generation/parsing paths. Verify how the --state flag and empty-state workaround are handled, then confirm that banks containing presets with state chunks can be created and parsed successfully.

Written by the indexing model from the issue text.