sched/fair: Add feature to toggle SchedTune utilization boosting

Sometimes we may want to use SchedTune boosting to bias tasks towards
higher-capacity CPUs without its influence on frequencies, which is
caused by its utilization-boosting behavior. For example, the CPU
frequencies may be managed by external frequency-based boosting
mechanisms.

To better accomodate for such scenarios and potentially reduce power
usage, add a togglable scheduler feature to control whether the
scheduler will artificially inflate the effective utilization of tasks
and CPUs that are under the effect of a SchedTune boost.

Signed-off-by: Danny Lin <danny@kdrag0n.dev>
Signed-off-by: Adam W. Willis <return.of.octobot@gmail.com>
Signed-off-by: Yaroslav Furman <yaro330@gmail.com>