[VZW P2P] Add atom max_inactivity_duration_sec.

This is for the for Carrier Roaming NB-IoT NTN module to track the maximum user inactivity duration of a satellite session.

Bug: 383033991
Test: atest
FLAG: com.android.internal.telephony.flags.carrier_roaming_nb_iot_ntn
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:058867e157e6726665d093e4c18e5f054db12d1b)
Merged-In: Ieb5b7dfd756e6ac370f336aae19b12360cf23f51
Change-Id: Ieb5b7dfd756e6ac370f336aae19b12360cf23f51