Add internal domain verification data classes

Eventually will be used to store state that's included as part of
com.android.server.pm.Settings.

Also adds equality and  Kotlin index operator mutation support to
SparseArray, to improve ease of use.

Exempt-From-Owner-Approval: Already approved by owners on main branch

Bug: 163565712
CTS-Coverage-Bug: 179382047

Test: none, will be tested as part of follow up change

Change-Id: Ie4eca3a99633465337758ee165e07f35c8db87c8