Add BLE sysprop "aggressive_connection_threshold"

When the number of ACL connections are less than this value,
aggressive connection parameter will be used.

Bug: 308483803
Bug: 378595485
Test: m -j;
Change-Id: Iddc753d49df02b64c7d7d7d14bb70563e0f6755d
diff --git a/private/property_contexts b/private/property_contexts
index 672a9ad..ace1470 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -703,6 +703,7 @@
 bluetooth.core.le.max_connection_interval_relaxed    u:object_r:bluetooth_config_prop:s0 exact uint
 bluetooth.core.le.min_connection_interval_aggressive u:object_r:bluetooth_config_prop:s0 exact uint
 bluetooth.core.le.max_connection_interval_aggressive u:object_r:bluetooth_config_prop:s0 exact uint
+bluetooth.core.le.aggressive_connection_threshold    u:object_r:bluetooth_config_prop:s0 exact uint
 bluetooth.core.le.connection_latency                 u:object_r:bluetooth_config_prop:s0 exact uint
 bluetooth.core.le.connection_supervision_timeout     u:object_r:bluetooth_config_prop:s0 exact uint
 bluetooth.core.le.direct_connection_timeout          u:object_r:bluetooth_config_prop:s0 exact uint