Can't list flags given an environment

[emyller]

Given an environment belongs to a project (e.g. flagsmith environments --project 000), I believe the following should work:

❯ flagsmith flag list --environment MySup3rC00lPr0j3ctK3y
Error: no project
Set --project, or `project` in flagsmith.json.

[khvn26]

We need to modify flagContext in internal/cmd/flags.go as follows:

• The project is known: keep the current sequence. There is no more API call, and no change for the user.
• The project is unknown, and the environment is set: call GetEnvironment. Read the project from the project field.
• The project is unknown, and the environment is not set, or the call returns 404: show the no project error. Add a hint that an environment name needs a project.

Noteworthy details:

1. The user can set the project and the environment together. If the key belongs to a different project, the CLI must show an error. The message environment %q not found in project %d is correct now, and this check must stay.
2. The environment get|update|delete|clone commands have the same problem. They take the environment as an argument, but they also ask for a project. The same change applies to them. The environment list command still needs a project.
3. If possible, we should avoid extending name cache with relationship data; it only exists to enhance entity display, and it must not control how the CLI finds an entity.
4. FLAGSMITH_ENVIRONMENT_KEY gets the same result, because resolveEnvironment uses this variable as an environment reference already.