leaudio: Minor refactor around connection state in native

This is preparation for the fix in the following patch, where we will
need to have better connection state information on the device

Bug: 251097804
Test: atest BluetoothInstrumentationTests
Tag: #feature
Merged-In: Ie83da88010ac03458d298a015bc857fecc945f96
Change-Id: Ie83da88010ac03458d298a015bc857fecc945f96
(cherry picked from commit 50a02fae)