Add support for explicit casts between signed and unsigned ints

[alamb]

Note: migrated from original JIRA: https://issues.apache.org/jira/browse/ARROW-8910

Add support for explicit casts between signed and unsigned ints.

Note that the type coercion optimizer rule shoud never implicity perform casts between types when data would be lost e.g. from negative value to unsigned type.

[alamb]

I think we have this feature today

https://arrow.apache.org/datafusion/user-guide/sql/data_types.html

We can also use arrow_cast if needed