Epic: Dependent flags

Flags being dependent on other flags has been requested several times.

One option for this would be to allow flag booleans/values to be used as segment operator values. So for example, if you wanted Flag B to only be enabled if Flag A is enabled:

- Create Flag A. Set as disabled.
- Create Flag B. Set as disabled.
- Create Segment. Single Rule: If Value of Flag A is set.
- Set a segment override on Flag B: If Segment set, override Flag B value to true.

## Cross-Project dependencies

We often get asked "Can we have a project with shared flags and a project with specific flags for e.g. iOS that combines both sets of flags". We could achieve this functionality with cross-project dependencies. Eg:

- Create a shared project and a flag `my_flag_1`
- Create an Android project
- Create an iOS project
- Create a flag in iOS and one in Android, `my_flag_1` and make it dependent on the shared project flag.

We've talked about this [here](https://github.com/Flagsmith/flagsmith/discussions/3767) but maybe the above solution would be sufficient