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ARROW-9447 [Rust][DataFusion] Made ScalarUDF (Send + Sync)

This allows udfs be declared dynamically from closures.

I found this necessary while declaring a scalarUDF that runs a closure that is declared non-statically.

Note that our current test passed because the closure did not move any value from outside and was thus coerced to `fn` as described under [RFC-1558](https://github.com/rust-lang/rfcs/blob/master/text/1558-closure-to-fn-coercion.md).

Closes #7740 from jorgecarleitao/thread_udfs

Authored-by: Jorge C. Leitao <jorgecarleitao@gmail.com>
Signed-off-by: Wes McKinney <wesm@apache.org>