Fix permission issue in GattService.clientConnect

Using `ActivityManager.getPackageImportance` instead of
`ActivityManager.getUidImportance` to fix permission issue when checking
foreground information during BLE connection. Also changing for server
connect.

Bug: 306525416
Test: atest BluetoothInstrumentationTests
Change-Id: I86e2cfd1d4503c9509922f5d0573d1543bcc1280