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ARROW-10685: [Rust] [DataFusion] Added support for Join on filter-pushdown optimizer.

This PR extends the filter pushdown optimizer to support nodes of multiple children. In the context of the `join`, this allows to push filters down the joins. E.g.

```
"\
Filter: #a LtEq Int64(1)\
\n  Join: a = a\
\n    TableScan: test projection=None\
\n    TableScan: test projection=None"
```

is optimized to

```
"\
Join: a = a\
\n  Filter: #a LtEq Int64(1)\
\n    TableScan: test projection=None\
\n  Filter: #a LtEq Int64(1)\
\n    TableScan: test projection=None"
```

This also reduces the complexity of the optimizer by making it perform a single pass on the plan.

Naturally, this has a major implication in performance as the `join` is an expensive operation.

Closes #8738 from jorgecarleitao/filter_push

Authored-by: Jorge C. Leitao <jorgecarleitao@gmail.com>
Signed-off-by: Andy Grove <andygrove73@gmail.com>