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ARROW-6694: [Rust] [DataFusion] Integration tests now use physical query plan

Integration tests now use physical query plan instead of executing directly from the logical plan.

As part of this PR I added the mapping from logical to physical plan for LIMIT which I somehow missed when creating the PR for the LIMIT physical plan.

Closes #5582 from andygrove/ARROW-6694 and squashes the following commits:

059f12f9e <Andy Grove> Add check for negative LIMIT when signed int is used
4b9c670dd <Andy Grove> remove another case of executing the logical plan
b13058e85 <Andy Grove> integration tests now use physical query plan

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