ANDROID: sched: Disable find_best_target() by default

Now that the mainline EAS wake-up path has been extended to cope with
prefer-idle tasks, the need for a dedicated Android-specific wake-up
routine (find_best_target()) becomes less clear. Indeed, main reasons
for introducting find_best_target() in the first place were:

  1. the energy_diff function was very slow, so we couldn't afford to
     use it on all CPUs for each wake-up for latency reasons;

  2. schedtune provides additional information about tasks (the
     prefer-idle flag in particular) which needed to be taken into
     account in the placement algorithm.

Now that the energy diff calculation is much faster (with the simplified
energy model) and that the EAS path is aware of prefer-idle tasks, there
is no clear reason to use find_best_target() any more.

So, let's disable it for now to minimize the amount of out-of-tree code
used in the scheduler. If using the mainline path doesn't cause
regressions, it is a good sign find_best_target() can be removed safely,
eventually. Otherwise, reverting back to the old behaviour is trivial
since this patch only changes the sched_feat default, but doesn't remove
the fbt() code path.

Bug: 120440300
Change-Id: Idb5d68a3c4af7d2212e0922ab6d9a089170b5e1c
Signed-off-by: Quentin Perret <quentin.perret@arm.com>