[analyzer] Improved checker naming in CFG dump.

This implements FIXME from Checker.cpp (FIXME: We want to return the package + name of the checker here.) and replaces hardcoded checker names with the new ones obtained via getCheckName().getName().

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201525 91177308-0d34-0410-b5e6-96231b3b80d8