Only apply the early network agent creation on B

...and if the feature is not killed.

For devices on V and below, this feature should be subject
to a rollout. That rollout should be done in mainline beta
if possible at all, meaning the flags can be defined later.

If beta isn't possible after all, a legacy rollout can happen
starting in M2025-06 too.

Test: manual
Change-Id: I941762bf759ce25b4bd1f908e971ceaf4f49f671
3 files changed