Set default value for carrier config KEY_UNDELIVERED_SMS_MESSAGE_EXPIRATION_TIME

This cl sets the default value (7 days which is used in
SmsBroadcastUndelivered) for carrier config
KEY_UNDELIVERED_SMS_MESSAGE_EXPIRATION_TIME.

Without default value, the configs will not be returned from APIs
like CarrierConigManager.getConfigForSub if default and carrier
config app doesn't override them. It may cause caller
process crash if not handled properly.

Bug: 261776046
Test: atest FrameworksTelephonyTests
Test: Basic phone functional test (activation/call/data/messages...)
Change-Id: I46085146605db27ef2d7d393917584a96aceb7fd