Use language tags to store Configuration's locale list.

Instead of storing each Locale within a Configuration object's locale
list by its language, country, variant, and script to proto, store the
entire locale list by its language tags representation which accurately
describes each locale.

Bug: 140197723
Test: atest ConfigurationTest
Test: atest UsageStatsDatabaseTest
Test: manually with bad data
Change-Id: I53946ed4e31de0ffe9c84875c391a7dec6f5375a