SQL integration tests named `mod`

[alamb]

Describe the bug
DataFusion has a large library of sql integration tests

They are currently run via

cargo test -p datafusion --test mod

(Or cargo test)

which is quite confusing as the name mod is somewhat silly. They used to be run via

cargo test -p datafusion --test sql

Expected behavior
Should run the test like this:

cargo test -p datafusion --test sql_integration

Additional context
I think this came in via #1491