[analyzer] Add more timers for performance profiling.

The -analyzer-stats flag now allows you to find out how much time was spent
on AST-based analysis and on path-sensitive analysis and, separately,
on bug visitors, as they're occasionally a performance problem on their own.

The total timer wasn't useful because there's anyway a total time printed out.
Remove it.

Differential Revision: https://reviews.llvm.org/D63227

llvm-svn: 364266