Bluetooth HAL: Add to foreground schedtune group

EAS (Energy-Aware Scheduler) tends to cluster tasks together unless
they're marked to prefer an idle CPU (prefer-idle) during placement.
This is to save energy however it increases latencies. This is
noticeable when the Binder driver demotes the RT task to CFS and when
we try to do load balance in this path, the selection path still selects
a busy CPU. Add Bluetooth HAL service to the foreground schedtune group
to fix this as its critical for tasks like bluetooth audio playback.

Test: Boot and verify bluetooth HAL is in the foreground stune group
Bug: 36867985

Change-Id: Ib3c43cca4a2049af3700978b58a05989cc20b6ac
Signed-off-by: Joel Fernandes <joelaf@google.com>