[zephyr] Drop BLE connection on endpoint close (#14600)
[zephyr] Drop BLE connection on endpoint close (#14600)

When a BLE endpoint is closed on the peripheral side, the
associated connection is not automatically closed. Instead,
BlePlatformDelegate::NotifyChipConnectionClosed() is called,
but the function is empty for Zephyr and many other
platforms.

Implement connection closing for Zephyr platform.

Signed-off-by: Damian Krolik <e2fe6fe1e6b356a130ab0d30147444bb6e61419d@nordicsemi.no>
project-chip/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip,nestlabs/connectedhomeip,nestlabs/connectedhomeip,nestlabs/connectedhomeip,nestlabs/connectedhomeip,nestlabs/connectedhomeip,nestlabs/connectedhomeip,project-chip/connectedhomeip,nestlabs/connectedhomeip,project-chip/connectedhomeip