[C++] add support for UnionArrays to Take and Filter

[asfimport]

The Take and Filter kernels do not currently support UnionArrays, but this should not be difficult to add

Reporter: Ben Kietzman / @bkietz
Assignee: Ben Kietzman / @bkietz

Related issues:

• [C++] Support concatenation of UnionArrays (is blocked by)
• [C++] Better support for building UnionArrays (is blocked by)
• [C++] Support take from UnionArray, ListArray, StructArray (is duplicated by)

PRs and other links:

• GitHub Pull Request #4866

_{Note: This issue was originally created as ARROW-5594. Please see the migration documentation for further details.}

[asfimport]

Ben Kietzman / @bkietz:
https://issues.apache.org/jira/browse/ARROW-4975

[asfimport]

Antoine Pitrou / @pitrou:
Issue resolved by pull request 4866
#4866