[MEP] Resolve port index in case apps are calling switchToSubscription(without...

[MEP] Resolve port index in case apps are calling switchToSubscription(without portIndex) API for disable operation.

Subscription enable/disable is done through a single EuiccManager.switchToSubscription API. If the passing subId is invalid which means to disable the currently enabled profile on eUICC. With MEP, there can be more than one active subscription so apps should explicitly calling new API switchToSubscripti.on(with portIndex) to specify disable which profile from eUICC.

Bug: 218393363
Test: atest FrameworksTelephonyTests
Change-Id: I8694cf2cbe6637ca4e1e44a4c12cf1126da2eca3