Extend and randomize BTA_DM_SWITCH_DELAY_TIMER_MS

This delay was designed to prevent role switch conflicts with
authentication. However, these conflicts can still occur and cause
pairing failure, especially on some old ChromeOS devices (MVL8897).

Extend it to at least 1000ms and randomize it to further decrease the
conflict rate.

Bug: 364202070
Bug: 388459732
Test: mmm packages/modules/Bluetooth
Test: Tauto multi-device tests
Flag: com.android.bluetooth.flags.extend_and_randomize_role_switch_delay
Change-Id: Id2080099b06c91c8318982c5a9e8a3dba14c144b