refactor(fuzzer): Refactor JoinFuzzer to allow multi-join plans (#12198)

Summary:

Generates a cascading multi-join from left to right with the inputs to the join being values nodes.

[t1, t2, t3, t4]
```
t1  t2
 \  /
  a   t3
   \  /
     b   t4
      \  /
        c
```

Reviewed By: kagamiori

Differential Revision: D68797355