[Resolver-log]: Some modifications for debug logging

 - Remove stdio.h from all files now that we're no longer using printf() etc
 - Use std::string to buffer the output and android::base::StringAppendF() to write into it.

Test: Test: make; flash; runtests.sh
Change-Id: Iea268dbf3e799c04b0812926ca8e381be213c9b4