Replace all printf's with ostream for efficiency in Showmap

Replace printf with ostream to avoid unnecessary string
concatenations.

Test: compare showmap output before and after the change.
Test: output before the change: https://paste.googleplex.com/6003405962084352
Test: output after the change: https://paste.googleplex.com/4841506847326208
Bug: 232840435
Change-Id: Icd156593279cb638189133124be8ce41b949fac6
1 file changed