EuiccSession: tell ApduSender to keep channel open after sending APDU if any session started.

This optimization is limited to eSIM download journey i.e. EuiccManager.downloadSubscription.

Bug: 335257880
Test: unit test
Test: manual - download eSIM and verify startSession/endSession log.
Test: QA result no regression b/335257880#comment15
Flag: com.android.internal.telephony.flags.optimization_apdu_sender
Change-Id: Ic6d7c4c6320ae45184df013236f16ca94ec211d0