Cleanup package_string() and its users

package_string() isn't readable in its current form and a loop is
unnecessary, so let's replace that with the direct calculations.  The
new and old functions are identical in results except an edge case
where the old function incorrectly believes it needs to round up to
'10' for the size prefix, when '9' would be ok, specifically:
10\naaaaa\n\f vs 9\naaaaa\n\f.  This is true for all powers of 10.

Clean up the calling side in logcat as well.

Test: printing log statistics and prune list works
Change-Id: Ib62ab2badab59040215b130ec9e3efbc7c95af3f