L2CAP: Store channel configuration state in a separate class

Introduce ChannelConfigurationState in SignallingManager. This handles
storing configuration related information.

Remove configuration logic in DynamicChannelImpl, so we can use the same
DynamicChannelImpl for both classic and LE.

Bug: 144503952
Test: bluetooth_test_gd
Change-Id: I7873516162bed4200086debd111244cb456b2601