Use MappedFile in android_database_SQLiteConnection

By using MappedFile, android_database_SQLiteConnection can compile on
all host platforms, including Windows. Also, MappedFile automatically
munmap's the memory region when it goes out of scope.

Test: Robolectric SQLiteDatabaseTest on Windows
Bug: 317884162
Change-Id: I535449c296e0a6fa0b3c16516de11efbf9623e59