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ARROW-6567: [Rust] [DataFusion] Wrap aggregate in projection when needed

This PR fixes a long standing bug where it was assumed that aggregate queries would always have a projection listing grouping expressions before aggregate expressions. The SQL query planner now wraps the aggregate query in a projection, when needed, to preserve the intended column order.

I also fixed a couple of non deterministic tests.

Closes #5639 from andygrove/ARROW-6567 and squashes the following commits:

46b9ee34a <Andy Grove> fix non deterministic tests
439f190b4 <Andy Grove> Wrap aggregate in projection if needed

Authored-by: Andy Grove <andygrove73@gmail.com>
Signed-off-by: Andy Grove <andygrove73@gmail.com>