[C++] Provide a simple reflection utility for {{struct}}s

[asfimport]

In cases such as ARROW-13025 it's advantageous to avoid boilerplate when dealing with objects which are basic structs of data members. A simple reflection utility (get/set the value of a data member, print the name of a member to string) would allow writing functionality generically in terms of a tuple of properties, greatly reducing boilerplate.

See a sketch of one such utility here https://gist.github.com/bkietz/7899f477e86df49f21ab17201c518d74

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

PRs and other links:

• GitHub Pull Request #10551

_{Note: This issue was originally created as ARROW-13097. Please see the migration documentation for further details.}

[asfimport]

Ben Kietzman / @bkietz:
Issue resolved by pull request 10551
#10551