Frontend: Add granular trait control for client-side SDKs

Support the new `allow_client_traits_in_evaluation` environment-level field in the Environment settings UI.

The Environment settings UI should now include a section that allows to define a policy in regards to traits sent over by client-side SDKs:
- The existing `allow_client_traits` should be controlled by the "Persist" toggle.
- The new `allow_client_traits_in_evaluation` field should be controlled by "Use in evaluation" toggle.
- Disabling "Use in evaluation" should disable the "Persist" toggle.

Update the docs accordingly.