InCallService: Stop hiding code in setter

When setting the headset or LeCall, it is confusing that the setter is
doing more than setting it.
By inlining the method, we remove this abstraction

Bug: 330247213
Fix: 330247213
Test: atest BluetoothInstrumentationTests:BluetoothInCallServiceTests
Flag: Exempt refactor
Change-Id: Ice096f0c02222b9b88d60fceeeea23d165d95d52