Reduce duplicate strings due to the package cache.

The following charts are the actual measurement with and without the fix,
using "dumpsys system".
- The red bar is "total private dirty".
- The X axsis is time since boot.

Without fix:
- First boot:
https://docs.google.com/spreadsheets/d/1R6lL0AnAp93HnrqWujJFNgOjj6wvGicgDlbDAevbc3g/edit#gid=0
Private dirty stabilizes at ~16.8M.

- Second boot:
https://docs.google.com/spreadsheets/d/1R6lL0AnAp93HnrqWujJFNgOjj6wvGicgDlbDAevbc3g/edit#gid=1918404197
Private dirty stabilizes at ~17.8M.

With fix:
- First boot:
https://docs.google.com/spreadsheets/d/1R6lL0AnAp93HnrqWujJFNgOjj6wvGicgDlbDAevbc3g/edit#gid=791764875
Private dirty stabilizes at ~17.0M.

- Second boot:
https://docs.google.com/spreadsheets/d/1R6lL0AnAp93HnrqWujJFNgOjj6wvGicgDlbDAevbc3g/edit#gid=1820894299
Private dirty stabilizes at ~17.0M.

Test: build, boot, reboot, adb-install, reboot
bit FrameworksCoreTests:android.content.pm.PackageParserTest

Bug: 64112468
Change-Id: I5ae9c1b2d021fe62526d4e0dd1a52a962b48206e