Moves to a read-only interface inside Computer and all of its
dependencies. This is the next step towards true data model
immutability and mutation time snapshots.
Bug: 202291449
Test: atest PackageManagerServiceUnitTests \
PackageManagerSettingsTests \
PackageUserStateTest \
PackageParserTest \
PackageManagerTest \
ScanTests \
PackageInfoUserFieldsTest \
DexoptUtilsTest \
PackageManagerComponentLabelIconOverrideTest
Change-Id: If5afb44e20b50a15b2b99057b0797c9b88e6e60b
b049d95ef8