[analyzer] Enable the new edge algorithm by default.

...but don't yet migrate over the existing plist tests. Some of these
would be trivial to migrate; others could use a bit of inspection first.
In any case, though, the new edge algorithm seems to have proven itself,
and we'd like more coverage (and more usage) of it going forwards.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@183165 91177308-0d34-0410-b5e6-96231b3b80d8