[analyzer] Pass external Dst set to NodeBuilder

This moves the responsibility for storing the output node set from the
builder to the clients. The builder is just responsible for transforming
an input set into the output set: {SrcSet/SrcNode} -> {Frontier}.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@142826 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed